Double-differential round trip time measurement

ABSTRACT

In an aspect, a position estimation entity may obtain a first differential round trip time (RTT) measurement based on a first RTT measurement between a user equipment (UE) and a first wireless node and a second RTT measurement between the UE and a second wireless node, may obtain a second differential RTT measurement based on a third RTT measurement between a third wireless node and the first wireless node and a fourth RTT measurement between the third wireless node and the second wireless node, and may determine a positioning estimate of the UE based at least in part on the first differential RTT measurement and the second differential RTT measurement.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present Application for Patent claims priority to Greek PatentApplication No. 20210100028, entitled “DOUBLE-DIFFERENTIAL ROUND TRIPTIME MEASUREMENT,” filed Jan. 14, 2021, and is a national stageapplication, filed under 35 U.S.C. § 371, of International PatentApplication No. PCT/US2022/011474, entitled “DOUBLE-DIFFERENTIAL ROUNDTRIP TIME MEASUREMENT,” filed Jan. 6, 2022, both of which are assignedto the assignee hereof and expressly incorporated herein by reference intheir entirety.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

Aspects of the disclosure relate generally to wireless communications,and more particularly to a double-differential round trip time (RTT)measurement.

2. Description of the Related Art

Wireless communication systems have developed through variousgenerations, including a first-generation analog wireless phone service(1G), a second-generation (2G) digital wireless phone service (includinginterim 2.5G networks), a third-generation (3G) high speed data,Internet-capable wireless service and a fourth-generation (4G) service(e.g., LTE or WiMax). There are presently many different types ofwireless communication systems in use, including cellular and personalcommunications service (PCS) systems. Examples of known cellular systemsinclude the cellular analog advanced mobile phone system (AMPS), anddigital cellular systems based on code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), the Global System for Mobile access (GSM) variation of TDMA,etc.

A fifth generation (5G) wireless standard, referred to as New Radio(NR), enables higher data transfer speeds, greater numbers ofconnections, and better coverage, among other improvements. The 5Gstandard, according to the Next Generation Mobile Networks Alliance, isdesigned to provide data rates of several tens of megabits per second toeach of tens of thousands of users, with 1 gigabit per second to tens ofworkers on an office floor. Several hundreds of thousands ofsimultaneous connections should be supported in order to support largewireless sensor deployments. Consequently, the spectral efficiency of 5Gmobile communications should be significantly enhanced compared to thecurrent 4G standard. Furthermore, signaling efficiencies should beenhanced and latency should be substantially reduced compared to currentstandards.

SUMMARY

The following presents a simplified summary relating to one or moreaspects disclosed herein. Thus, the following summary should not beconsidered an extensive overview relating to all contemplated aspects,nor should the following summary be considered to identify key orcritical elements relating to all contemplated aspects or to delineatethe scope associated with any particular aspect. Accordingly, thefollowing summary has the sole purpose to present certain conceptsrelating to one or more aspects relating to the mechanisms disclosedherein in a simplified form to precede the detailed descriptionpresented below.

In an aspect, a method of operating a position estimation entityincludes: obtaining a first differential round trip time (RTT)measurement based on a first RTT measurement between a user equipment(UE) and a first wireless node and a second RTT measurement between theUE and a second wireless node; obtaining a second differential RTTmeasurement based on a third RTT measurement between a third wirelessnode and the first wireless node and a fourth RTT measurement betweenthe third wireless node and the second wireless node; and determining apositioning estimate of the UE based at least in part on the firstdifferential RTT measurement and the second differential RTTmeasurement.

In some aspects, the first differential RTT measurement is triggered bythe position estimation entity separately from the second differentialRTT measurement.

In some aspects, the first differential RTT measurement is triggered ata first frequency or based on a first triggering event, and the seconddifferential RTT measurement is triggered at a second frequency or basedon a second triggering event.

In some aspects, the first differential RTT measurement is triggered inresponse to a determination to perform the positioning estimate of theUE, and the second differential RTT measurement is triggered in responseto a determination to calibrate a hardware group delay of the firstwireless node, the second wireless node, or both.

In some aspects, the first wireless node, the second wireless node andthe third wireless node are associated with respective known locationsbefore the determination of the position estimate.

In some aspects, the first wireless node, the second wireless node andthe third wireless node include one or more positioning reference units(PRUs).

In some aspects, the first wireless node, the second wireless node andthe third wireless node comprise one or more base stations, one or moreanchor user equipments (UEs), or a combination thereof.

In some aspects, the first wireless node, the second wireless node andthe third wireless node each correspond to a respective base station.

In some aspects, the third RTT measurement is based on one or morepositioning reference signals (PRSs) exchanged between the firstwireless node and the third wireless node on one or more fixed beams, orthe fourth RTT measurement is based on at least one PRS exchangedbetween the second wireless node and the third wireless node on at leastone fixed beam, or a combination thereof.

In some aspects, the first wireless node, the second wireless node andthe third wireless node each correspond to a respective UE.

In some aspects, the first wireless node and the second wireless nodecorrespond to base stations and the third wireless node corresponds toan anchor UE associated with a known location.

In some aspects, positioning resources allocated for determination of alocation of the anchor UE are greater than positioning resources usedfor determination of the positioning estimate of the UE.

In some aspects, the third RTT measurement is based on a firstpositioning reference signal (PRS) from the third wireless node to thefirst wireless node and a second PRS from the first wireless node to thethird wireless node.

In some aspects, the first PRS and the second PRS are associated withthe same PRS type.

In some aspects, the first PRS and the second PRS comprise at least onesingle symbol PRS, at least one multi-symbol PRS, or a combinationthereof.

In some aspects, the fourth RTT measurement is based on a third PRS fromthe third wireless node to the second wireless node and a fourth PRSfrom the second wireless node to the third wireless node.

In some aspects, the first PRS corresponds to the third PRS, or thefirst PRS and the second PRS are different.

In some aspects, the method includes transmitting a message to the firstwireless node and the third wireless node, the message indicatingwhether the first PRS follows the second PRS or whether the second PRSfollows the first PRS.

In some aspects, the method includes transmitting a message to the firstwireless node and the third wireless node, the message indicating a PRSresource to be used for an initial PRS of the third RTT measurement.

In some aspects, the first, second, third and fourth RTT measurementsand/or the first differential RTT measurement and the seconddifferential RTT measurement are received at the position estimationentity via one or more measurement reports.

In some aspects, the one or more measurement reports each indicate, fora respective measurement, a transmission reception point (TRP)identifier a positioning reference signal (PRS) source identifier, a PRSresource set ID, a frequency layer ID, a time stamp, or a combinationthereof.

In some aspects, the first differential RTT measurement is based on atleast one additional RTT measurement between the UE and at least oneadditional wireless node, wherein the second differential RTTmeasurement is based on one or more additional RTT measurements betweenthe third wireless node and one or more additional wireless nodes, or acombination thereof.

In some aspects, the method includes obtaining a third differential RTTmeasurement based on a fifth RTT measurement between a fourth wirelessnode and the first wireless node and a sixth RTT measurement between thefourth wireless node and the second wireless node; and using the thirddifferential RTT measurement to determine the positioning estimate.

In some aspects, the method includes receiving, from the first wirelessnode, the second wireless node, or both, an indication of a firsthardware group delay calibration capability, wherein the seconddifferential RTT measurement is triggered in response to the firsthardware group delay calibration capability.

In some aspects, the first hardware group delay calibration capabilityis a dynamic indication or a static or semi-static indication.

In some aspects, another positioning estimate for another UE isdetermined based on a single differential RTT measurement based onwireless nodes involved with the another positioning estimate beingassociated with a second hardware group delay calibration capabilitythat is more accurate than the first hardware group delay calibrationcapability.

In some aspects, the method includes receiving, from the first wirelessnode, the second wireless node, or both, a request to trigger the seconddifferential RTT measurement for hardware group delay calibration.

In some aspects, the method includes selecting the third wireless nodefor hardware group delay calibration of the first wireless node and thesecond wireless node via the second RTT differential measurement basedon one or more parameters.

In some aspects, the one or more parameters comprise channel conditionsbetween the third wireless node and the first wireless node and thesecond wireless node.

In some aspects, the selection of the third wireless node ispredetermined if each of the first wireless node, the second wirelessnode and the third wireless node are stationary nodes, and the selectionof the third wireless node is dynamic if one or more of the firstwireless node, the second wireless node and the third wireless node aremobile nodes.

In an aspect, a position estimation entity includes: a memory; at leastone transceiver; and at least one processor communicatively coupled tothe memory and the at least one transceiver, the at least one processorconfigured to: obtain a first differential round trip time (RTT)measurement based on a first RTT measurement between a user equipment(UE) and a first wireless node and a second RTT measurement between theUE and a second wireless node; obtain a second differential RTTmeasurement based on a third RTT measurement between a third wirelessnode and the first wireless node and a fourth RTT measurement betweenthe third wireless node and the second wireless node; and determine apositioning estimate of the UE based at least in part on the firstdifferential RTT measurement and the second differential RTTmeasurement.

In an aspect, a position estimation entity includes: means for obtaininga first differential round trip time (RTT) measurement based on a firstRTT measurement between a user equipment (UE) and a first wireless nodeand a second RTT measurement between the UE and a second wireless node;means for obtaining a second differential RTT measurement based on athird RTT measurement between a third wireless node and the firstwireless node and a fourth RTT measurement between the third wirelessnode and the second wireless node; and means for determining apositioning estimate of the UE based at least in part on the firstdifferential RTT measurement and the second differential RTTmeasurement.

In an aspect, a non-transitory computer-readable medium storing a set ofinstructions includes one or more instructions that, when executed byone or more processors of a position estimation entity, cause theposition estimation entity to: obtain a first differential round triptime (RTT) measurement based on a first RTT measurement between a userequipment (UE) and a first wireless node and a second RTT measurementbetween the UE and a second wireless node; obtain a second differentialRTT measurement based on a third RTT measurement between a thirdwireless node and the first wireless node and a fourth RTT measurementbetween the third wireless node and the second wireless node; anddetermine a positioning estimate of the UE based at least in part on thefirst differential RTT measurement and the second differential RTTmeasurement.

Other objects and advantages associated with the aspects disclosedherein will be apparent to those skilled in the art based on theaccompanying drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofvarious aspects of the disclosure and are provided solely forillustration of the aspects and not limitation thereof

FIG. 1 illustrates an exemplary wireless communications system,according to various aspects.

FIGS. 2A and 2B illustrate example wireless network structures,according to various aspects.

FIGS. 3A to 3C are simplified block diagrams of several sample aspectsof components that may be employed in wireless communication nodes andconfigured to support communication as taught herein.

FIGS. 4A and 4B are diagrams illustrating examples of frame structuresand channels within the frame structures, according to aspects of thedisclosure.

FIG. 5 illustrates an exemplary PRS configuration for a cell supportedby a wireless node.

FIG. 6 illustrates an exemplary wireless communications system accordingto various aspects of the disclosure.

FIG. 7 illustrates an exemplary wireless communications system accordingto various aspects of the disclosure.

FIG. 8A is a graph showing the RF channel response at a receiver overtime according to aspects of the disclosure.

FIG. 8B is a diagram illustrating this separation of clusters in AoD.

FIG. 9 is a diagram showing exemplary timings of RTT measurement signalsexchanged between a base station and a UE, according to aspects of thedisclosure.

FIG. 10 is a diagram showing exemplary timings of RTT measurementsignals exchanged between a base station and a UE, according to otheraspects of the disclosure.

FIG. 11 illustrates an exemplary wireless communications systemaccording to aspects of the disclosure.

FIG. 12 illustrates is a diagram showing exemplary timings of RTTmeasurement signals exchanged between a base station (e.g., any of thebase stations described herein) and a UE (e.g., any of the UEs describedherein), according to other aspects of the disclosure.

FIG. 13 illustrates a diagram depicting a satellite-based positioningscheme.

FIG. 14 illustrates a diagram depicting another satellite-basedpositioning scheme.

FIG. 15 illustrates a diagram depicting another satellite-basedpositioning scheme.

FIG. 16 illustrates an exemplary process of wireless communication,according to aspects of the disclosure.

FIG. 17 illustrates an example implementation of the process of FIG. 16in accordance with an aspect of the disclosure.

FIG. 18 illustrates an example implementation of the process of FIG. 16in accordance with an aspect of the disclosure.

FIG. 19 illustrates an example implementation of the process of FIG. 16in accordance with an aspect of the disclosure.

DETAILED DESCRIPTION

Aspects of the disclosure are provided in the following description andrelated drawings directed to various examples provided for illustrationpurposes. Alternate aspects may be devised without departing from thescope of the disclosure. Additionally, well-known elements of thedisclosure will not be described in detail or will be omitted so as notto obscure the relevant details of the disclosure.

The words “exemplary” and/or “example” are used herein to mean “servingas an example, instance, or illustration.” Any aspect described hereinas “exemplary” and/or “example” is not necessarily to be construed aspreferred or advantageous over other aspects. Likewise, the term“aspects of the disclosure” does not require that all aspects of thedisclosure include the discussed feature, advantage or mode ofoperation.

Those of skill in the art will appreciate that the information andsignals described below may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the description below may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof, depending inpart on the particular application, in part on the desired design, inpart on the corresponding technology, etc.

Further, many aspects are described in terms of sequences of actions tobe performed by, for example, elements of a computing device. It will berecognized that various actions described herein can be performed byspecific circuits (e.g., application specific integrated circuits(ASICs)), by program instructions being executed by one or moreprocessors, or by a combination of both. Additionally, the sequence(s)of actions described herein can be considered to be embodied entirelywithin any form of non-transitory computer-readable storage mediumhaving stored therein a corresponding set of computer instructions that,upon execution, would cause or instruct an associated processor of adevice to perform the functionality described herein. Thus, the variousaspects of the disclosure may be embodied in a number of differentforms, all of which have been contemplated to be within the scope of theclaimed subject matter. In addition, for each of the aspects describedherein, the corresponding form of any such aspects may be describedherein as, for example, “logic configured to” perform the describedaction.

As used herein, the terms “user equipment” (UE) and “base station” arenot intended to be specific or otherwise limited to any particular radioaccess technology (RAT), unless otherwise noted. In general, a UE may beany wireless communication device (e.g., a mobile phone, router, tabletcomputer, laptop computer, consumer or consumer asset tracking device,wearable (e.g., smartwatch, glasses, augmented reality (AR)/virtualreality (VR) headset, etc.), vehicle (e.g., automobile, motorcycle,bicycle, etc.), Internet of Things (IoT) device, etc.) used by a user tocommunicate over a wireless communications network. A UE may be mobileor may (e.g., at certain times) be stationary, and may communicate witha radio access network (RAN). As used herein, the term “UE” may bereferred to interchangeably as an “access terminal” or “AT,” a “clientdevice,” a “wireless device,” a “subscriber device,” a “subscriberterminal,” a “subscriber station,” a “user terminal” or UT, a “mobileterminal,” a “mobile station,” or variations thereof. Generally, UEs cancommunicate with a core network via a RAN, and through the core networkthe UEs can be connected with external networks such as the Internet andwith other UEs. Of course, other mechanisms of connecting to the corenetwork and/or the Internet are also possible for the UEs, such as overwired access networks, wireless local area network (WLAN) networks(e.g., based on IEEE 802.11, etc.) and so on.

A base station may operate according to one of several RATs incommunication with UEs depending on the network in which it is deployed,and may be alternatively referred to as an access point (AP), a networknode, a NodeB, an evolved NodeB (eNB), a New Radio (NR) Node B (alsoreferred to as a gNB or gNodeB), etc. In addition, in some systems abase station may provide purely edge node signaling functions while inother systems it may provide additional control and/or networkmanagement functions. In some systems, a base station may correspond toa Customer Premise Equipment (CPE) or a road-side unit (RSU). In somedesigns, a base station may correspond to a high-powered UE (e.g., avehicle UE or VUE) that may provide limited certain infrastructurefunctionality. A communication link through which UEs can send signalsto a base station is called an uplink (UL) channel (e.g., a reversetraffic channel, a reverse control channel, an access channel, etc.). Acommunication link through which the base station can send signals toUEs is called a downlink (DL) or forward link channel (e.g., a pagingchannel, a control channel, a broadcast channel, a forward trafficchannel, etc.). As used herein the term traffic channel (TCH) can referto either an UL/reverse or DL/forward traffic channel.

The term “base station” may refer to a single physicaltransmission-reception point (TRP) or to multiple physical TRPs that mayor may not be co-located. For example, where the term “base station”refers to a single physical TRP, the physical TRP may be an antenna ofthe base station corresponding to a cell of the base station. Where theterm “base station” refers to multiple co-located physical TRPs, thephysical TRPs may be an array of antennas (e.g., as in a multiple-inputmultiple-output (MIMO) system or where the base station employsbeamforming) of the base station. Where the term “base station” refersto multiple non-co-located physical TRPs, the physical TRPs may be adistributed antenna system (DAS) (a network of spatially separatedantennas connected to a common source via a transport medium) or aremote radio head (RRH) (a remote base station connected to a servingbase station). Alternatively, the non-co-located physical TRPs may bethe serving base station receiving the measurement report from the UEand a neighbor base station whose reference RF signals the UE ismeasuring. Because a TRP is the point from which a base stationtransmits and receives wireless signals, as used herein, references totransmission from or reception at a base station are to be understood asreferring to a particular TRP of the base station.

An “RF signal” comprises an electromagnetic wave of a given frequencythat transports information through the space between a transmitter anda receiver. As used herein, a transmitter may transmit a single “RFsignal” or multiple “RF signals” to a receiver. However, the receivermay receive multiple “RF signals” corresponding to each transmitted RFsignal due to the propagation characteristics of RF signals throughmultipath channels. The same transmitted RF signal on different pathsbetween the transmitter and receiver may be referred to as a “multipath”RF signal.

According to various aspects, FIG. 1 illustrates an exemplary wirelesscommunications system 100. The wireless communications system 100 (whichmay also be referred to as a wireless wide area network (WWAN)) mayinclude various base stations 102 and various UEs 104. The base stations102 may include macro cell base stations (high power cellular basestations) and/or small cell base stations (low power cellular basestations). In an aspect, the macro cell base station may include eNBswhere the wireless communications system 100 corresponds to an LTEnetwork, or gNBs where the wireless communications system 100corresponds to a NR network, or a combination of both, and the smallcell base stations may include femtocells, picocells, microcells, etc.

The base stations 102 may collectively form a RAN and interface with acore network 170 (e.g., an evolved packet core (EPC) or next generationcore (NGC)) through backhaul links 122, and through the core network 170to one or more location servers 172. In addition to other functions, thebase stations 102 may perform functions that relate to one or more oftransferring user data, radio channel ciphering and deciphering,integrity protection, header compression, mobility control functions(e.g., handover, dual connectivity), inter-cell interferencecoordination, connection setup and release, load balancing, distributionfor non-access stratum (NAS) messages, NAS node selection,synchronization, RAN sharing, multimedia broadcast multicast service(MBMS), subscriber and equipment trace, RAN information management(RIM), paging, positioning, and delivery of warning messages. The basestations 102 may communicate with each other directly or indirectly(e.g., through the EPC/NGC) over backhaul links 134, which may be wiredor wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Eachof the base stations 102 may provide communication coverage for arespective geographic coverage area 110. In an aspect, one or more cellsmay be supported by a base station 102 in each coverage area 110. A“cell” is a logical communication entity used for communication with abase station (e.g., over some frequency resource, referred to as acarrier frequency, component carrier, carrier, band, or the like), andmay be associated with an identifier (e.g., a physical cell identifier(PCI), a virtual cell identifier (VCI)) for distinguishing cellsoperating via the same or a different carrier frequency. In some cases,different cells may be configured according to different protocol types(e.g., machine-type communication (MTC), narrowband IoT (NB-IoT),enhanced mobile broadband (eMBB), or others) that may provide access fordifferent types of UEs. Because a cell is supported by a specific basestation, the term “cell” may refer to either or both the logicalcommunication entity and the base station that supports it, depending onthe context. In some cases, the term “cell” may also refer to ageographic coverage area of a base station (e.g., a sector), insofar asa carrier frequency can be detected and used for communication withinsome portion of geographic coverage areas 110.

While neighboring macro cell base station 102 geographic coverage areas110 may partially overlap (e.g., in a handover region), some of thegeographic coverage areas 110 may be substantially overlapped by alarger geographic coverage area 110. For example, a small cell basestation 102′ may have a coverage area 110′ that substantially overlapswith the coverage area 110 of one or more macro cell base stations 102.A network that includes both small cell and macro cell base stations maybe known as a heterogeneous network. A heterogeneous network may alsoinclude home eNBs (HeNBs), which may provide service to a restrictedgroup known as a closed subscriber group (CSG).

The communication links 120 between the base stations 102 and the UEs104 may include UL (also referred to as reverse link) transmissions froma UE 104 to a base station 102 and/or downlink (DL) (also referred to asforward link) transmissions from a base station 102 to a UE 104. Thecommunication links 120 may use MIMO antenna technology, includingspatial multiplexing, beamforming, and/or transmit diversity. Thecommunication links 120 may be through one or more carrier frequencies.Allocation of carriers may be asymmetric with respect to DL and UL(e.g., more or less carriers may be allocated for DL than for UL).

The wireless communications system 100 may further include a wirelesslocal area network (WLAN) access point (AP) 150 in communication withWLAN stations (STAs) 152 via communication links 154 in an unlicensedfrequency spectrum (e.g., 5 GHz). When communicating in an unlicensedfrequency spectrum, the WLAN STAs 152 and/or the WLAN AP 150 may performa clear channel assessment (CCA) or listen before talk (LBT) procedureprior to communicating in order to determine whether the channel isavailable.

The small cell base station 102′ may operate in a licensed and/or anunlicensed frequency spectrum. When operating in an unlicensed frequencyspectrum, the small cell base station 102′ may employ LTE or NRtechnology and use the same 5 GHz unlicensed frequency spectrum as usedby the WLAN AP 150. The small cell base station 102′, employing LTE/5Gin an unlicensed frequency spectrum, may boost coverage to and/orincrease capacity of the access network. NR in unlicensed spectrum maybe referred to as NR-U. LTE in an unlicensed spectrum may be referred toas LTE-U, licensed assisted access (LAA), or MulteFire.

The wireless communications system 100 may further include a millimeterwave (mmW) base station 180 that may operate in mmW frequencies and/ornear mmW frequencies in communication with a UE 182. Extremely highfrequency (EHF) is part of the RF in the electromagnetic spectrum. EHFhas a range of 30 GHz to 300 GHz and a wavelength between 1 millimeterand 10 millimeters. Radio waves in this band may be referred to as amillimeter wave. Near mmW may extend down to a frequency of 3 GHz with awavelength of 100 millimeters. The super high frequency (SHF) bandextends between 3 GHz and 30 GHz, also referred to as centimeter wave.Communications using the mmW/near mmW radio frequency band have highpath loss and a relatively short range. The mmW base station 180 and theUE 182 may utilize beamforming (transmit and/or receive) over a mmWcommunication link 184 to compensate for the extremely high path lossand short range. Further, it will be appreciated that in alternativeconfigurations, one or more base stations 102 may also transmit usingmmW or near mmW and beamforming. Accordingly, it will be appreciatedthat the foregoing illustrations are merely examples and should not beconstrued to limit the various aspects disclosed herein.

Transmit beamforming is a technique for focusing an RF signal in aspecific direction. Traditionally, when a network node (e.g., a basestation) broadcasts an RF signal, it broadcasts the signal in alldirections (omni-directionally). With transmit beamforming, the networknode determines where a given target device (e.g., a UE) is located(relative to the transmitting network node) and projects a strongerdownlink RF signal in that specific direction, thereby providing afaster (in terms of data rate) and stronger RF signal for the receivingdevice(s). To change the directionality of the RF signal whentransmitting, a network node can control the phase and relativeamplitude of the RF signal at each of the one or more transmitters thatare broadcasting the RF signal. For example, a network node may use anarray of antennas (referred to as a “phased array” or an “antennaarray”) that creates a beam of RF waves that can be “steered” to pointin different directions, without actually moving the antennas.Specifically, the RF current from the transmitter is fed to theindividual antennas with the correct phase relationship so that theradio waves from the separate antennas add together to increase theradiation in a desired direction, while cancelling to suppress radiationin undesired directions.

Transmit beams may be quasi-collocated, meaning that they appear to thereceiver (e.g., a UE) as having the same parameters, regardless ofwhether or not the transmitting antennas of the network node themselvesare physically collocated. In NR, there are four types ofquasi-collocation (QCL) relations. Specifically, a QCL relation of agiven type means that certain parameters about a second reference RFsignal on a second beam can be derived from information about a sourcereference RF signal on a source beam. Thus, if the source reference RFsignal is QCL Type A, the receiver can use the source reference RFsignal to estimate the Doppler shift, Doppler spread, average delay, anddelay spread of a second reference RF signal transmitted on the samechannel. If the source reference RF signal is QCL Type B, the receivercan use the source reference RF signal to estimate the Doppler shift andDoppler spread of a second reference RF signal transmitted on the samechannel. If the source reference RF signal is QCL Type C, the receivercan use the source reference RF signal to estimate the Doppler shift andaverage delay of a second reference RF signal transmitted on the samechannel. If the source reference RF signal is QCL Type D, the receivercan use the source reference RF signal to estimate the spatial receiveparameter of a second reference RF signal transmitted on the samechannel.

In receive beamforming, the receiver uses a receive beam to amplify RFsignals detected on a given channel. For example, the receiver canincrease the gain setting and/or adjust the phase setting of an array ofantennas in a particular direction to amplify (e.g., to increase thegain level of) the RF signals received from that direction. Thus, when areceiver is said to beamform in a certain direction, it means the beamgain in that direction is high relative to the beam gain along otherdirections, or the beam gain in that direction is the highest comparedto the beam gain in that direction of all other receive beams availableto the receiver. This results in a stronger received signal strength(e.g., reference signal received power (RSRP), reference signal receivedquality (RSRQ), signal-to-interference-plus-noise ratio (SINR), etc.) ofthe RF signals received from that direction.

Receive beams may be spatially related. A spatial relation means thatparameters for a transmit beam for a second reference signal can bederived from information about a receive beam for a first referencesignal. For example, a UE may use a particular receive beam to receive areference downlink reference signal (e.g., synchronization signal block(SSB)) from a base station. The UE can then form a transmit beam forsending an uplink reference signal (e.g., sounding reference signal(SRS)) to that base station based on the parameters of the receive beam.

Note that a “downlink” beam may be either a transmit beam or a receivebeam, depending on the entity forming it. For example, if a base stationis forming the downlink beam to transmit a reference signal to a UE, thedownlink beam is a transmit beam. If the UE is forming the downlinkbeam, however, it is a receive beam to receive the downlink referencesignal. Similarly, an “uplink” beam may be either a transmit beam or areceive beam, depending on the entity forming it. For example, if a basestation is forming the uplink beam, it is an uplink receive beam, and ifa UE is forming the uplink beam, it is an uplink transmit beam.

In 5G, the frequency spectrum in which wireless nodes (e.g., basestations 102/180, UEs 104/182) operate is divided into multiplefrequency ranges, FR1 (from 450 to 6000 MHz), FR2 (from 24250 to 52600MHz), FR3 (above 52600 MHz), and FR4(between FR1 and FR2). In amulti-carrier system, such as 5G, one of the carrier frequencies isreferred to as the “primary carrier” or “anchor carrier” or “primaryserving cell” or “PCell,” and the remaining carrier frequencies arereferred to as “secondary carriers” or “secondary serving cells” or“SCells.” In carrier aggregation, the anchor carrier is the carrieroperating on the primary frequency (e.g., FR1) utilized by a UE 104/182and the cell in which the UE 104/182 either performs the initial radioresource control (RRC) connection establishment procedure or initiatesthe RRC connection re-establishment procedure. The primary carriercarries all common and UE-specific control channels, and may be acarrier in a licensed frequency (however, this is not always the case).A secondary carrier is a carrier operating on a second frequency (e.g.,FR2) that may be configured once the RRC connection is establishedbetween the UE 104 and the anchor carrier and that may be used toprovide additional radio resources. In some cases, the secondary carriermay be a carrier in an unlicensed frequency. The secondary carrier maycontain only necessary signaling information and signals, for example,those that are UE-specific may not be present in the secondary carrier,since both primary uplink and downlink carriers are typicallyUE-specific. This means that different UEs 104/182 in a cell may havedifferent downlink primary carriers. The same is true for the uplinkprimary carriers. The network is able to change the primary carrier ofany UE 104/182 at any time. This is done, for example, to balance theload on different carriers. Because a “serving cell” (whether a PCell oran SCell) corresponds to a carrier frequency/component carrier overwhich some base station is communicating, the term “cell,” “servingcell,” “component carrier,” “carrier frequency,” and the like can beused interchangeably.

For example, still referring to FIG. 1 , one of the frequencies utilizedby the macro cell base stations 102 may be an anchor carrier (or“PCell”) and other frequencies utilized by the macro cell base stations102 and/or the mmW base station 180 may be secondary carriers(“SCells”). The simultaneous transmission and/or reception of multiplecarriers enables the UE 104/182 to significantly increase its datatransmission and/or reception rates. For example, two 20 MHz aggregatedcarriers in a multi-carrier system would theoretically lead to atwo-fold increase in data rate (i.e., 40 MHz), compared to that attainedby a single 20 MHz carrier.

The wireless communications system 100 may further include one or moreUEs, such as UE 190, that connects indirectly to one or morecommunication networks via one or more device-to-device (D2D)peer-to-peer (P2P) links. In the example of FIG. 1 , UE 190 has a D2DP2P link 192 with one of the UEs 104 connected to one of the basestations 102 (e.g., through which UE 190 may indirectly obtain cellularconnectivity) and a D2D P2P link 194 with WLAN STA 152 connected to theWLAN AP 150 (through which UE 190 may indirectly obtain WLAN-basedInternet connectivity). In an example, the D2D P2P links 192 and 194 maybe supported with any well-known D2D RAT, such as LTE Direct (LTE-D),WiFi Direct (WiFi-D), Bluetooth®, and so on.

The wireless communications system 100 may further include a UE 164 thatmay communicate with a macro cell base station 102 over a communicationlink 120 and/or the mmW base station 180 over a mmW communication link184. For example, the macro cell base station 102 may support a PCelland one or more SCells for the UE 164 and the mmW base station 180 maysupport one or more SCells for the UE 164.

According to various aspects, FIG. 2A illustrates an example wirelessnetwork structure 200. For example, an NGC 210 (also referred to as a“5GC”) can be viewed functionally as control plane functions 214 (e.g.,UE registration, authentication, network access, gateway selection,etc.) and user plane functions 212, (e.g., UE gateway function, accessto data networks, IP routing, etc.) which operate cooperatively to formthe core network. User plane interface (NG-U) 213 and control planeinterface (NG-C) 215 connect the gNB 222 to the NGC 210 and specificallyto the control plane functions 214 and user plane functions 212. In anadditional configuration, an eNB 224 may also be connected to the NGC210 via NG-C 215 to the control plane functions 214 and NG-U 213 to userplane functions 212. Further, eNB 224 may directly communicate with gNB222 via a backhaul connection 223. In some configurations, the New RAN220 may only have one or more gNBs 222, while other configurationsinclude one or more of both eNBs 224 and gNBs 222. Either gNB 222 or eNB224 may communicate with UEs 204 (e.g., any of the UEs depicted in FIG.1 ). Another optional aspect may include location server 230, which maybe in communication with the NGC 210 to provide location assistance forUEs 204. The location server 230 can be implemented as a plurality ofseparate servers (e.g., physically separate servers, different softwaremodules on a single server, different software modules spread acrossmultiple physical servers, etc.), or alternately may each correspond toa single server. The location server 230 can be configured to supportone or more location services for UEs 204 that can connect to thelocation server 230 via the core network, NGC 210, and/or via theInternet (not illustrated). Further, the location server 230 may beintegrated into a component of the core network, or alternatively may beexternal to the core network.

According to various aspects, FIG. 2B illustrates another examplewireless network structure 250. For example, an NGC 260 (also referredto as a “5GC”) can be viewed functionally as control plane functions,provided by an access and mobility management function (AMF)/user planefunction (UPF) 264, and user plane functions, provided by a sessionmanagement function (SMF) 262, which operate cooperatively to form thecore network (i.e., NGC 260). User plane interface 263 and control planeinterface 265 connect the eNB 224 to the NGC 260 and specifically to SMF262 and AMF/UPF 264, respectively. In an additional configuration, a gNB222 may also be connected to the NGC 260 via control plane interface 265to AMF/UPF 264 and user plane interface 263 to SMF 262. Further, eNB 224may directly communicate with gNB 222 via the backhaul connection 223,with or without gNB direct connectivity to the NGC 260. In someconfigurations, the New RAN 220 may only have one or more gNBs 222,while other configurations include one or more of both eNBs 224 and gNBs222. Either gNB 222 or eNB 224 may communicate with UEs 204 (e.g., anyof the UEs depicted in FIG. 1 ). The base stations of the New RAN 220communicate with the AMF-side of the AMF/UPF 264 over the N2 interfaceand the UPF-side of the AMF/UPF 264 over the N3 interface.

The functions of the AMF include registration management, connectionmanagement, reachability management, mobility management, lawfulinterception, transport for session management (SM) messages between theUE 204 and the SMF 262, transparent proxy services for routing SMmessages, access authentication and access authorization, transport forshort message service (SMS) messages between the UE 204 and the shortmessage service function (SMSF) (not shown), and security anchorfunctionality (SEAF). The AMF also interacts with the authenticationserver function (AUSF) (not shown) and the UE 204, and receives theintermediate key that was established as a result of the UE 204authentication process. In the case of authentication based on a UMTS(universal mobile telecommunications system) subscriber identity module(USIM), the AMF retrieves the security material from the AUSF. Thefunctions of the AMF also include security context management (SCM). TheSCM receives a key from the SEAF that it uses to derive access-networkspecific keys. The functionality of the AMF also includes locationservices management for regulatory services, transport for locationservices messages between the UE 204 and the location managementfunction (LMF) 270, as well as between the New RAN 220 and the LMF 270,evolved packet system (EPS) bearer identifier allocation forinterworking with the EPS, and UE 204 mobility event notification. Inaddition, the AMF also supports functionalities for non-3GPP accessnetworks.

Functions of the UPF include acting as an anchor point forintra-/inter-RAT mobility (when applicable), acting as an externalprotocol data unit (PDU) session point of interconnect to the datanetwork (not shown), providing packet routing and forwarding, packetinspection, user plane policy rule enforcement (e.g., gating,redirection, traffic steering), lawful interception (user planecollection), traffic usage reporting, quality of service (QoS) handlingfor the user plane (e.g., UL/DL rate enforcement, reflective QoS markingin the DL), UL traffic verification (service data flow (SDF) to QoS flowmapping), transport level packet marking in the UL and DL, DL packetbuffering and DL data notification triggering, and sending andforwarding of one or more “end markers” to the source RAN node.

The functions of the SMF 262 include session management, UE Internetprotocol (IP) address allocation and management, selection and controlof user plane functions, configuration of traffic steering at the UPF toroute traffic to the proper destination, control of part of policyenforcement and QoS, and downlink data notification. The interface overwhich the SMF 262 communicates with the AMF-side of the AMF/UPF 264 isreferred to as the N11 interface.

Another optional aspect may include a LMF 270, which may be incommunication with the NGC 260 to provide location assistance for UEs204. The LMF 270 can be implemented as a plurality of separate servers(e.g., physically separate servers, different software modules on asingle server, different software modules spread across multiplephysical servers, etc.), or alternately may each correspond to a singleserver. The LMF 270 can be configured to support one or more locationservices for UEs 204 that can connect to the LMF 270 via the corenetwork, NGC 260, and/or via the Internet (not illustrated).

FIGS. 3A, 3B, and 3C illustrate several sample components (representedby corresponding blocks) that may be incorporated into a UE 302 (whichmay correspond to any of the UEs described herein), a base station 304(which may correspond to any of the base stations described herein), anda network entity 306 (which may correspond to or embody any of thenetwork functions described herein, including the location server 230and the LMF 270) to support the file transmission operations as taughtherein. It will be appreciated that these components may be implementedin different types of apparatuses in different implementations (e.g., inan ASIC, in a system-on-chip (SoC), etc.). The illustrated componentsmay also be incorporated into other apparatuses in a communicationsystem. For example, other apparatuses in a system may includecomponents similar to those described to provide similar functionality.Also, a given apparatus may contain one or more of the components. Forexample, an apparatus may include multiple transceiver components thatenable the apparatus to operate on multiple carriers and/or communicatevia different technologies.

The UE 302 and the base station 304 each include wireless wide areanetwork (WWAN) transceiver 310 and 350, respectively, configured tocommunicate via one or more wireless communication networks (not shown),such as an NR network, an LTE network, a GSM network, and/or the like.The WWAN transceivers 310 and 350 may be connected to one or moreantennas 316 and 356, respectively, for communicating with other networknodes, such as other UEs, access points, base stations (e.g., eNBs,gNBs), etc., via at least one designated RAT (e.g., NR, LTE, GSM, etc.)over a wireless communication medium of interest (e.g., some set oftime/frequency resources in a particular frequency spectrum). The WWANtransceivers 310 and 350 may be variously configured for transmittingand encoding signals 318 and 358 (e.g., messages, indications,information, and so on), respectively, and, conversely, for receivingand decoding signals 318 and 358 (e.g., messages, indications,information, pilots, and so on), respectively, in accordance with thedesignated RAT. Specifically, the transceivers 310 and 350 include oneor more transmitters 314 and 354, respectively, for transmitting andencoding signals 318 and 358, respectively, and one or more receivers312 and 352, respectively, for receiving and decoding signals 318 and358, respectively.

The UE 302 and the base station 304 also include, at least in somecases, wireless local area network (WLAN) transceivers 320 and 360,respectively. The WLAN transceivers 320 and 360 may be connected to oneor more antennas 326 and 366, respectively, for communicating with othernetwork nodes, such as other UEs, access points, base stations, etc.,via at least one designated RAT (e.g., WiFi, LTE-D, Bluetooth®, etc.)over a wireless communication medium of interest. The WLAN transceivers320 and 360 may be variously configured for transmitting and encodingsignals 328 and 368 (e.g., messages, indications, information, and soon), respectively, and, conversely, for receiving and decoding signals328 and 368 (e.g., messages, indications, information, pilots, and soon), respectively, in accordance with the designated RAT. Specifically,the transceivers 320 and 360 include one or more transmitters 324 and364, respectively, for transmitting and encoding signals 328 and 368,respectively, and one or more receivers 322 and 362, respectively, forreceiving and decoding signals 328 and 368, respectively.

Transceiver circuitry including a transmitter and a receiver maycomprise an integrated device (e.g., embodied as a transmitter circuitand a receiver circuit of a single communication device) in someimplementations, may comprise a separate transmitter device and aseparate receiver device in some implementations, or may be embodied inother ways in other implementations. In an aspect, a transmitter mayinclude or be coupled to a plurality of antennas (e.g., antennas 316,336, and 376), such as an antenna array, that permits the respectiveapparatus to perform transmit “beamforming,” as described herein.Similarly, a receiver may include or be coupled to a plurality ofantennas (e.g., antennas 316, 336, and 376), such as an antenna array,that permits the respective apparatus to perform receive beamforming, asdescribed herein. In an aspect, the transmitter and receiver may sharethe same plurality of antennas (e.g., antennas 316, 336, and 376), suchthat the respective apparatus can only receive or transmit at a giventime, not both at the same time. A wireless communication device (e.g.,one or both of the transceivers 310 and 320 and/or 350 and 360) of theapparatuses 302 and/or 304 may also comprise a network listen module(NLM) or the like for performing various measurements.

The apparatuses 302 and 304 also include, at least in some cases,satellite positioning systems (SPS) receivers 330 and 370. The SPSreceivers 330 and 370 may be connected to one or more antennas 336 and376, respectively, for receiving SPS signals 338 and 378, respectively,such as global positioning system (GPS) signals, global navigationsatellite system (GLONASS) signals, Galileo signals, Beidou signals,Indian Regional Navigation Satellite System (NAVIC), Quasi-ZenithSatellite System (QZSS), etc. The SPS receivers 330 and 370 may compriseany suitable hardware and/or software for receiving and processing SPSsignals 338 and 378, respectively. The SPS receivers 330 and 370 requestinformation and operations as appropriate from the other systems, andperforms calculations necessary to determine the apparatus' 302 and 304positions using measurements obtained by any suitable SPS algorithm.

The base station 304 and the network entity 306 each include at leastone network interfaces 380 and 390 for communicating with other networkentities. For example, the network interfaces 380 and 390 (e.g., one ormore network access ports) may be configured to communicate with one ormore network entities via a wire-based or wireless backhaul connection.In some aspects, the network interfaces 380 and 390 may be implementedas transceivers configured to support wire-based or wireless signalcommunication. This communication may involve, for example, sending andreceiving: messages, parameters, or other types of information.

The apparatuses 302, 304, and 306 also include other components that maybe used in conjunction with the operations as disclosed herein. The UE302 includes processor circuitry implementing a processing system 332for providing functionality relating to, for example, false base station(FBS) detection as disclosed herein and for providing other processingfunctionality. The base station 304 includes a processing system 384 forproviding functionality relating to, for example, FBS detection asdisclosed herein and for providing other processing functionality. Thenetwork entity 306 includes a processing system 394 for providingfunctionality relating to, for example, FBS detection as disclosedherein and for providing other processing functionality. In an aspect,the processing systems 332, 384, and 394 may include, for example, oneor more general purpose processors, multi-core processors, ASICs,digital signal processors (DSPs), field programmable gate arrays (FPGA),or other programmable logic devices or processing circuitry.

The apparatuses 302, 304, and 306 include memory circuitry implementingmemory components 340, 386, and 396 (e.g., each including a memorydevice), respectively, for maintaining information (e.g., informationindicative of reserved resources, thresholds, parameters, and so on). Insome cases, the apparatuses 302, 304, and 306 may include positioningmodules 342, 388 and 389, respectively. The positioning modules 342, 388and 389 may be hardware circuits that are part of or coupled to theprocessing systems 332, 384, and 394, respectively, that, when executed,cause the apparatuses 302, 304, and 306 to perform the functionalitydescribed herein. Alternatively, the positioning modules 342, 388 and389 may be memory modules (as shown in FIGS. 3A-C) stored in the memorycomponents 340, 386, and 396, respectively, that, when executed by theprocessing systems 332, 384, and 394, cause the apparatuses 302, 304,and 306 to perform the functionality described herein.

The UE 302 may include one or more sensors 344 coupled to the processingsystem 332 to provide movement and/or orientation information that isindependent of motion data derived from signals received by the WWANtransceiver 310, the WLAN transceiver 320, and/or the GPS receiver 330.By way of example, the sensor(s) 344 may include an accelerometer (e.g.,a micro-electrical mechanical systems (MEMS) device), a gyroscope, ageomagnetic sensor (e.g., a compass), an altimeter (e.g., a barometricpressure altimeter), and/or any other type of movement detection sensor.Moreover, the sensor(s) 344 may include a plurality of different typesof devices and combine their outputs in order to provide motioninformation. For example, the sensor(s) 344 may use a combination of amulti-axis accelerometer and orientation sensors to provide the abilityto compute positions in 2D and/or 3D coordinate systems.

In addition, the UE 302 includes a user interface 346 for providingindications (e.g., audible and/or visual indications) to a user and/orfor receiving user input (e.g., upon user actuation of a sensing devicesuch a keypad, a touch screen, a microphone, and so on). Although notshown, the apparatuses 304 and 306 may also include user interfaces.

Referring to the processing system 384 in more detail, in the downlink,IP packets from the network entity 306 may be provided to the processingsystem 384. The processing system 384 may implement functionality for anRRC layer, a packet data convergence protocol (PDCP) layer, a radio linkcontrol (RLC) layer, and a medium access control (MAC) layer. Theprocessing system 384 may provide RRC layer functionality associatedwith broadcasting of system information (e.g., master information block(MIB), system information blocks (SIBs)), RRC connection control (e.g.,RRC connection paging, RRC connection establishment, RRC connectionmodification, and RRC connection release), inter-RAT mobility, andmeasurement configuration for UE measurement reporting; PDCP layerfunctionality associated with header compression/decompression, security(ciphering, deciphering, integrity protection, integrity verification),and handover support functions; RLC layer functionality associated withthe transfer of upper layer packet data units (PDUs), error correctionthrough ARQ, concatenation, segmentation, and reassembly of RLC servicedata units (SDUs), re-segmentation of RLC data PDUs, and reordering ofRLC data PDUs; and MAC layer functionality associated with mappingbetween logical channels and transport channels, scheduling informationreporting, error correction, priority handling, and logical channelprioritization.

The transmitter 354 and the receiver 352 may implement Layer-1functionality associated with various signal processing functions.Layer-1, which includes a physical (PHY) layer, may include errordetection on the transport channels, forward error correction (FEC)coding/decoding of the transport channels, interleaving, rate matching,mapping onto physical channels, modulation/demodulation of physicalchannels, and MIMO antenna processing. The transmitter 354 handlesmapping to signal constellations based on various modulation schemes(e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying(QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation(M-QAM)). The coded and modulated symbols may then be split intoparallel streams. Each stream may then be mapped to an orthogonalfrequency division multiplexing (OFDM) subcarrier, multiplexed with areference signal (e.g., pilot) in the time and/or frequency domain, andthen combined together using an Inverse Fast Fourier Transform (IFFT) toproduce a physical channel carrying a time domain OFDM symbol stream.The OFDM stream is spatially precoded to produce multiple spatialstreams. Channel estimates from a channel estimator may be used todetermine the coding and modulation scheme, as well as for spatialprocessing. The channel estimate may be derived from a reference signaland/or channel condition feedback transmitted by the UE 302. Eachspatial stream may then be provided to one or more different antennas356. The transmitter 354 may modulate an RF carrier with a respectivespatial stream for transmission.

At the UE 302, the receiver 312 receives a signal through its respectiveantenna(s) 316. The receiver 312 recovers information modulated onto anRF carrier and provides the information to the processing system 332.The transmitter 314 and the receiver 312 implement Layer-1 functionalityassociated with various signal processing functions. The receiver 312may perform spatial processing on the information to recover any spatialstreams destined for the UE 302. If multiple spatial streams aredestined for the UE 302, they may be combined by the receiver 312 into asingle OFDM symbol stream. The receiver 312 then converts the OFDMsymbol stream from the time-domain to the frequency domain using a fastFourier transform (FFT). The frequency domain signal comprises aseparate OFDM symbol stream for each subcarrier of the OFDM signal. Thesymbols on each subcarrier, and the reference signal, are recovered anddemodulated by determining the most likely signal constellation pointstransmitted by the base station 304. These soft decisions may be basedon channel estimates computed by a channel estimator. The soft decisionsare then decoded and de-interleaved to recover the data and controlsignals that were originally transmitted by the base station 304 on thephysical channel. The data and control signals are then provided to theprocessing system 332, which implements Layer-3 and Layer-2functionality.

In the UL, the processing system 332 provides demultiplexing betweentransport and logical channels, packet reassembly, deciphering, headerdecompression, and control signal processing to recover IP packets fromthe core network. The processing system 332 is also responsible forerror detection.

Similar to the functionality described in connection with the DLtransmission by the base station 304, the processing system 332 providesRRC layer functionality associated with system information (e.g., MIB,SIBS) acquisition, RRC connections, and measurement reporting; PDCPlayer functionality associated with header compression/decompression,and security (ciphering, deciphering, integrity protection, integrityverification); RLC layer functionality associated with the transfer ofupper layer PDUs, error correction through ARQ, concatenation,segmentation, and reassembly of RLC SDUs, re-segmentation of RLC dataPDUs, and reordering of RLC data PDUs; and MAC layer functionalityassociated with mapping between logical channels and transport channels,multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing ofMAC SDUs from TBs, scheduling information reporting, error correctionthrough HARQ, priority handling, and logical channel prioritization.

Channel estimates derived by the channel estimator from a referencesignal or feedback transmitted by the base station 304 may be used bythe transmitter 314 to select the appropriate coding and modulationschemes, and to facilitate spatial processing. The spatial streamsgenerated by the transmitter 314 may be provided to different antenna(s)316. The transmitter 314 may modulate an RF carrier with a respectivespatial stream for transmission.

The UL transmission is processed at the base station 304 in a mannersimilar to that described in connection with the receiver function atthe UE 302. The receiver 352 receives a signal through its respectiveantenna(s) 356. The receiver 352 recovers information modulated onto anRF carrier and provides the information to the processing system 384.

In the UL, the processing system 384 provides demultiplexing betweentransport and logical channels, packet reassembly, deciphering, headerdecompression, control signal processing to recover IP packets from theUE 302. IP packets from the processing system 384 may be provided to thecore network. The processing system 384 is also responsible for errordetection.

For convenience, the apparatuses 302, 304, and/or 306 are shown in FIGS.3A-C as including various components that may be configured according tothe various examples described herein. It will be appreciated, however,that the illustrated blocks may have different functionality indifferent designs.

The various components of the apparatuses 302, 304, and 306 maycommunicate with each other over data buses 334, 382, and 392,respectively. The components of FIGS. 3A-C may be implemented in variousways. In some implementations, the components of FIGS. 3A-C may beimplemented in one or more circuits such as, for example, one or moreprocessors and/or one or more ASICs (which may include one or moreprocessors). Here, each circuit may use and/or incorporate at least onememory component for storing information or executable code used by thecircuit to provide this functionality. For example, some or all of thefunctionality represented by blocks 310 to 346 may be implemented byprocessor and memory component(s) of the UE 302 (e.g., by execution ofappropriate code and/or by appropriate configuration of processorcomponents). Similarly, some or all of the functionality represented byblocks 350 to 388 may be implemented by processor and memorycomponent(s) of the base station 304 (e.g., by execution of appropriatecode and/or by appropriate configuration of processor components). Also,some or all of the functionality represented by blocks 390 to 396 may beimplemented by processor and memory component(s) of the network entity306 (e.g., by execution of appropriate code and/or by appropriateconfiguration of processor components). For simplicity, variousoperations, acts, and/or functions are described herein as beingperformed “by a UE,” “by a base station,” “by a positioning entity,”etc. However, as will be appreciated, such operations, acts, and/orfunctions may actually be performed by specific components orcombinations of components of the UE, base station, positioning entity,etc., such as the processing systems 332, 384, 394, the transceivers310, 320, 350, and 360, the memory components 340, 386, and 396, thepositioning modules 342, 388 and 389, etc.

FIG. 4A is a diagram 400 illustrating an example of a DL framestructure, according to aspects of the disclosure. FIG. 4B is a diagram430 illustrating an example of channels within the DL frame structure,according to aspects of the disclosure. Other wireless communicationstechnologies may have a different frame structures and/or differentchannels.

LTE, and in some cases NR, utilizes OFDM on the downlink andsingle-carrier frequency division multiplexing (SC-FDM) on the uplink.Unlike LTE, however, NR has an option to use OFDM on the uplink as well.OFDM and SC-FDM partition the system bandwidth into multiple (K)orthogonal subcarriers, which are also commonly referred to as tones,bins, etc. Each subcarrier may be modulated with data. In general,modulation symbols are sent in the frequency domain with OFDM and in thetime domain with SC-FDM. The spacing between adjacent subcarriers may befixed, and the total number of subcarriers (K) may be dependent on thesystem bandwidth. For example, the spacing of the subcarriers may be 15kHz and the minimum resource allocation (resource block) may be 12subcarriers (or 180 kHz). Consequently, the nominal FFT size may beequal to 128, 256, 512, 1024, or 2048 for system bandwidth of 1.25, 2.5,5, 10, or 20 megahertz (MHz), respectively. The system bandwidth mayalso be partitioned into subbands. For example, a subband may cover 1.08MHz (i.e., 6 resource blocks), and there may be 1, 2, 4, 8, or 16subbands for system bandwidth of 1.25, 2.5, 5, 10, or 20 MHz,respectively.

LTE supports a single numerology (subcarrier spacing, symbol length,etc.). In contrast NR may support multiple numerologies, for example,subcarrier spacing of 15 kHz, 30 kHz, 60 kHz, 120 kHz and 204 kHz orgreater may be available. Table 1 provided below lists some variousparameters for different NR numerologies.

TABLE 1 Max. nominal Subcarrier slots/ Symbol system BW spacing Symbols/sub- slots/ slot duration (MHz) with (kHz) slot frame frame (ms) (μs) 4KFFT size 15 14 1 10 1 66.7 50 30 14 2 20 0.5 33.3 100 60 14 4 40 0.2516.7 100 120 14 8 80 0.125 8.33 400 240 14 16 160 0.0625 4.17 800

In the examples of FIGS. 4A and 4B, a numerology of 15 kHz is used.Thus, in the time domain, a frame (e.g., 10 ms) is divided into 10equally sized subframes of 1 ms each, and each subframe includes onetime slot. In FIGS. 4A and 4B, time is represented horizontally (e.g.,on the X axis) with time increasing from left to right, while frequencyis represented vertically (e.g., on the Y axis) with frequencyincreasing (or decreasing) from bottom to top.

A resource grid may be used to represent time slots, each time slotincluding one or more time concurrent resource blocks (RBs) (alsoreferred to as physical RBs (PRBs)) in the frequency domain. Theresource grid is further divided into multiple resource elements (REs).An RE may correspond to one symbol length in the time domain and onesubcarrier in the frequency domain. In the numerology of FIGS. 4A and4B, for a normal cyclic prefix, an RB may contain 12 consecutivesubcarriers in the frequency domain and 7 consecutive symbols (for DL,OFDM symbols; for UL, SC-FDMA symbols) in the time domain, for a totalof 84 REs. For an extended cyclic prefix, an RB may contain 12consecutive subcarriers in the frequency domain and 6 consecutivesymbols in the time domain, for a total of 72 REs. The number of bitscarried by each RE depends on the modulation scheme.

As illustrated in FIG. 4A, some of the REs carry DL reference (pilot)signals (DL-RS) for channel estimation at the UE. The DL-RS may includedemodulation reference signals (DMRS) and channel state informationreference signals (CSI-RS), exemplary locations of which are labeled “R”in FIG. 4A.

FIG. 4B illustrates an example of various channels within a DL subframeof a frame. The physical downlink control channel (PDCCH) carries DLcontrol information (DCI) within one or more control channel elements(CCEs), each CCE including nine RE groups (REGs), each REG includingfour consecutive REs in an OFDM symbol. The DCI carries informationabout UL resource allocation (persistent and non-persistent) anddescriptions about DL data transmitted to the UE. Multiple (e.g., up to8) DCIs can be configured in the PDCCH, and these DCIs can have one ofmultiple formats. For example, there are different DCI formats for ULscheduling, for non-MIMO DL scheduling, for MIMO DL scheduling, and forUL power control.

A primary synchronization signal (PSS) is used by a UE to determinesubframe/symbol timing and a physical layer identity. A secondarysynchronization signal (SSS) is used by a UE to determine a physicallayer cell identity group number and radio frame timing. Based on thephysical layer identity and the physical layer cell identity groupnumber, the UE can determine a PCI. Based on the PCI, the UE candetermine the locations of the aforementioned DL-RS. The physicalbroadcast channel (PBCH), which carries an MIB, may be logically groupedwith the PSS and SSS to form an SSB (also referred to as an SS/PBCH).The MIB provides a number of RBs in the DL system bandwidth and a systemframe number (SFN). The physical downlink shared channel (PDSCH) carriesuser data, broadcast system information not transmitted through the PBCHsuch as system information blocks (SIBs), and paging messages.

In some cases, the DL RS illustrated in FIG. 4A may be positioningreference signals (PRS). FIG. 5 illustrates an exemplary PRSconfiguration 500 for a cell supported by a wireless node (such as abase station 102). FIG. 5 shows how PRS positioning occasions aredetermined by a system frame number (SFN), a cell specific subframeoffset (Δ_(PRS)) 552, and the PRS periodicity (T_(PRS)) 520. Typically,the cell specific PRS subframe configuration is defined by a “PRSConfiguration Index” I_(PRS) included in observed time difference ofarrival (OTDOA) assistance data. The PRS periodicity (T_(PRS)) 520 andthe cell specific subframe offset (Δ_(PRS)) are defined based on the PRSconfiguration index I_(PRS), as illustrated in Table 2 below.

TABLE 2 PRS PRS PRS subframe configuration Index periodicity T_(PRS)offset Δ_(PRS) I_(PRS) (subframes) (subframes)  0-159 160 I_(PRS)160-479 320 I_(PRS) − 160  480-1119 640 I_(PRS) − 480 1120-2399 1280I_(PRS) − 1120 2400-2404 5 I_(PRS) − 2400 2405-2414 10 I_(PRS) − 24052415-2434 20 I_(PRS) − 2415 2435-2474 40 I_(PRS) − 2435 2475-2554 80I_(PRS) − 2475 2555-4095 Reserved

A PRS configuration is defined with reference to the SFN of a cell thattransmits PRS. PRS instances, for the first subframe of the N_(PRS)downlink subframes comprising a first PRS positioning occasion, maysatisfy:

(10×n _(f) +∈n _(s)/2┘−ΔΔ_(PRS))mod T_(PRS)=0,   Equation (1)

where n_(f) the SFN with 0≤n_(f)≤1023, n_(s) is the slot number withinthe radio frame defined by n_(f) with 0≤n_(s)≤19, TPRS is the PRSperiodicity 520, and Δ_(PRS) is the cell-specific subframe offset 552.

As shown in FIG. 5 , the cell specific subframe offset Δ_(PRS) 552 maybe defined in terms of the number of subframes transmitted starting fromsystem frame number 0 (Slot ‘Number 0’, marked as slot 550) to the startof the first (subsequent) PRS positioning occasion. In the example inFIG. 5 , the number of consecutive positioning subframes (N_(PRS)) ineach of the consecutive PRS positioning occasions 518 a, 518 b, and 518c equals 4. That is, each shaded block representing PRS positioningoccasions 518 a, 518 b, and 518 c represents four subframes.

In some aspects, when a UE receives a PRS configuration index I_(PRS) inthe OTDOA assistance data for a particular cell, the UE may determinethe PRS periodicity T_(PRS) 520 and PRS subframe offset Δ_(PRS) usingTable 2. The UE may then determine the radio frame, subframe, and slotwhen a PRS is scheduled in the cell (e.g., using Equation (1)). TheOTDOA assistance data may be determined by, for example, the locationserver (e.g., location server 230, LMF 270), and includes assistancedata for a reference cell, and a number of neighbor cells supported byvarious base stations.

Typically, PRS occasions from all cells in a network that use the samefrequency are aligned in time and may have a fixed known time offset(e.g., cell-specific subframe offset 552) relative to other cells in thenetwork that use a different frequency. In SFN-synchronous networks, allwireless nodes (e.g., base stations 102) may be aligned on both frameboundary and system frame number. Therefore, in SFN-synchronousnetworks, all cells supported by the various wireless nodes may use thesame PRS configuration index for any particular frequency of PRStransmission. On the other hand, in SFN-asynchronous networks, thevarious wireless nodes may be aligned on a frame boundary, but notsystem frame number. Thus, in SFN-asynchronous networks the PRSconfiguration index for each cell may be configured separately by thenetwork so that PRS occasions align in time.

UE may determine the timing of the PRS occasions of the reference andneighbor cells for OTDOA positioning, if the UE can obtain the celltiming (e.g., SFN) of at least one of the cells, e.g., the referencecell or a serving cell. The timing of the other cells may then bederived by the UE based, for example, on the assumption that PRSoccasions from different cells overlap.

A collection of resource elements that are used for transmission of PRSis referred to as a “PRS resource.” The collection of resource elementscan span multiple PRBs in the frequency domain and N (e.g., 1 or more)consecutive symbol(s) within a slot in the time domain. In a given OFDMsymbol, a PRS resource occupies consecutive PRBs. A PRS resource isdescribed by at least the following parameters: PRS resource identifier(ID), sequence ID, comb size-N, resource element offset in the frequencydomain, starting slot and starting symbol, number of symbols per PRSresource (i.e., the duration of the PRS resource), and QCL information(e.g., QCL with other DL reference signals). In some designs, oneantenna port is supported. The comb size indicates the number ofsubcarriers in each symbol carrying PRS. For example, a comb-size ofcomb-4 means that every fourth subcarrier of a given symbol carries PRS.

A “PRS resource set” is a set of PRS resources used for the transmissionof PRS signals, where each PRS resource has a PRS resource ID. Inaddition, the PRS resources in a PRS resource set are associated withthe same transmission-reception point (TRP). A PRS resource ID in a PRSresource set is associated with a single beam transmitted from a singleTRP (where a TRP may transmit one or more beams). That is, each PRSresource of a PRS resource set may be transmitted on a different beam,and as such, a “PRS resource” can also be referred to as a “beam.” Notethat this does not have any implications on whether the TRPs and thebeams on which PRS are transmitted are known to the UE. A “PRS occasion”is one instance of a periodically repeated time window (e.g., a group ofone or more consecutive slots) where PRS are expected to be transmitted.A PRS occasion may also be referred to as a “PRS positioning occasion,”a “positioning occasion,” or simply an “occasion.”

Note that the terms “positioning reference signal” and “PRS” maysometimes refer to specific reference signals that are used forpositioning in LTE or NR systems. However, as used herein, unlessotherwise indicated, the terms “positioning reference signal” and “PRS”refer to any type of reference signal that can be used for positioning,such as but not limited to, PRS signals in LTE or NR, navigationreference signals (NRSs) in 5G, transmitter reference signals (TRSs),cell-specific reference signals (CRSs), channel state informationreference signals (CSI-RSs), primary synchronization signals (PSSs),secondary synchronization signals (SSSs), SSB, etc.

An SRS is an uplink-only signal that a UE transmits to help the basestation obtain the channel state information (CSI) for each user.Channel state information describes how an RF signal propagates from theUE to the base station and represents the combined effect of scattering,fading, and power decay with distance. The system uses the SRS forresource scheduling, link adaptation, massive MIMO, beam management,etc.

Several enhancements over the previous definition of SRS have beenproposed for SRS for positioning (SRS-P), such as a new staggeredpattern within an SRS resource, a new comb type for SRS, new sequencesfor SRS, a higher number of SRS resource sets per component carrier, anda higher number of SRS resources per component carrier. In addition, theparameters “SpatialRelationlnfo” and “PathLossReference” are to beconfigured based on a DL RS from a neighboring TRP. Further still, oneSRS resource may be transmitted outside the active bandwidth part (BWP),and one SRS resource may span across multiple component carriers.Lastly, the UE may transmit through the same transmit beam from multipleSRS resources for UL-AoA. All of these are features that are additionalto the current SRS framework, which is configured through RRC higherlayer signaling (and potentially triggered or activated through MACcontrol element (CE) or downlink control information (DCI)).

As noted above, SRSs in NR are UE-specifically configured referencesignals transmitted by the UE used for the purposes of the sounding theuplink radio channel. Similar to CSI-RS, such sounding provides variouslevels of knowledge of the radio channel characteristics. On oneextreme, the SRS can be used at the gNB simply to obtain signal strengthmeasurements, e.g., for the purposes of UL beam management. On the otherextreme, SRS can be used at the gNB to obtain detailed amplitude andphase estimates as a function of frequency, time and space. In NR,channel sounding with SRS supports a more diverse set of use casescompared to LTE (e.g., downlink CSI acquisition for reciprocity-basedgNB transmit beamforming (downlink MIMO); uplink CSI acquisition forlink adaptation and codebook/non-codebook based precoding for uplinkMIMO, uplink beam management, etc.).

The SRS can be configured using various options. The time/frequencymapping of an SRS resource is defined by the following characteristics.

-   -   Time duration N_(symb) ^(SRS)—The time duration of an SRS        resource can be 1, 2, or 4 consecutive OFDM symbols within a        slot, in contrast to LTE which allows only a single OFDM symbol        per slot.    -   Starting symbol location 1₀—The starting symbol of an SRS        resource can be located anywhere within the last 6 OFDM symbols        of a slot provided the resource does not cross the end-of-slot        boundary.    -   Repetition factor R—For an SRS resource configured with        frequency hopping, repetition allows the same set of subcarriers        to be sounded in R consecutive OFDM symbols before the next hop        occurs (as used herein, a “hop” refers to specifically to a        frequency hop). For example, values of R are 1, 2, 4 where        R≤N_(symb) ^(SRS).    -   Transmission comb spacing K_(TC) and comb offset k_(TC)—An SRS        resource may occupy resource elements (REs) of a frequency        domain comb structure, where the comb spacing is either 2 or 4        REs like in LTE. Such a structure allows frequency domain        multiplexing of different SRS resources of the same or different        users on different combs, where the different combs are offset        from each other by an integer number of REs. The comb offset is        defined with respect to a PRB boundary, and can take values in        the range 0,1, . . . , K_(TC)-1 REs. Thus, for comb spacing        K_(TC)=2, there are 2 different combs available for multiplexing        if needed, and for comb spacing K_(TC)=4, there are 4 different        available combs.    -   Periodicity and slot offset for the case of        periodic/semi-persistent SRS.    -   Sounding bandwidth within a bandwidth part.

For low latency positioning, a gNB may trigger a UL SRS-P via a DCI(e.g., transmitted SRS-P may include repetition or beam-sweeping toenable several gNBs to receive the SRS-P). Alternatively, the gNB maysend information regarding aperiodic PRS transmission to the UE (e.g.,this configuration may include information about PRS from multiple gNBsto enable the UE to perform timing computations for positioning(UE-based) or for reporting (UE-assisted). While various embodiments ofthe present disclosure relate to DL PRS-based positioning procedures,some or all of such embodiments may also apply to UL SRS-P-basedpositioning procedures.

Note that the terms “sounding reference signal”, “SRS” and “SRS-P” maysometimes refer to specific reference signals that are used forpositioning in LTE or NR systems. However, as used herein, unlessotherwise indicated, the terms “sounding reference signal”, “SRS” and“SRS-P” refer to any type of reference signal that can be used forpositioning, such as but not limited to, SRS signals in LTE or NR,navigation reference signals (NRSs) in 5G, transmitter reference signals(TRSs), random access channel (RACH) signals for positioning (e.g., RACHpreambles, such as Msg-1 in 4-Step RACH procedure or Msg-A in 2-StepRACH procedure), etc.

3GPP Rel. 16 introduced various NR positioning aspects directed toincrease location accuracy of positioning schemes that involvemeasurement(s) associated with one or more UL or DL PRSs (e.g., higherbandwidth (BW), FR2 beam-sweeping, angle-based measurements such asAngle of Arrival (AoA) and Angle of Departure (AoD) measurements,multi-cell Round-Trip Time (RTT) measurements, etc.). If latencyreduction is a priority, then UE-based positioning techniques (e.g.,DL-only techniques without UL location measurement reporting) aretypically used. However, if latency is less of a concern, thenUE-assisted positioning techniques can be used, whereby UE-measured datais reported to a network entity (e.g., location server 230, LMF 270,etc.). Latency associated UE-assisted positioning techniques can bereduced somewhat by implementing the LMF in the RAN.

Layer-3 (L3) signaling (e.g., RRC or Location Positioning Protocol(LPP)) is typically used to transport reports that compriselocation-based data in association with UE-assisted positioningtechniques. L3 signaling is associated with relatively high latency(e.g., above 100 ms) compared with Layer-1 (L1, or PHY layer) signalingor Layer-2 (L2, or MAC layer) signaling. In some cases, lower latency(e.g., less than 100 ms, less than 10 ms, etc.) between the UE and theRAN for location-based reporting may be desired. In such cases, L3signaling may not be capable of reaching these lower latency levels. L3signaling of positioning measurements may comprise any combination ofthe following:

-   -   One or multiple TOA, TDOA, RSRP or Rx-Tx measurements,    -   One or multiple AoA/AoD (e.g., currently agreed only for        gNB->LMF reporting DL AoA and UL AoD) measurements,    -   One or multiple Multipath reporting measurements, e.g., per-path        ToA, RSRP, AoA/AoD (e.g., currently only per-path ToA allowed in        LTE)    -   One or multiple motion states (e.g., walking, driving, etc.) and        trajectories (e.g., currently for UE), and/or    -   One or multiple report quality indications.

More recently, L1 and L2 signaling has been contemplated for use inassociation with PRS-based reporting. For example, L1 and L2 signalingis currently used in some systems to transport CSI reports (e.g.,reporting of Channel Quality Indications (CQIs), Precoding MatrixIndicators (PMIs), Layer Indicators (Lis), L1-RSRP, etc.). CSI reportsmay comprise a set of fields in a pre-defined order (e.g., defined bythe relevant standard). A single UL transmission (e.g., on PUSCH orPUCCH) may include multiple reports, referred to herein as‘sub-reports’, which are arranged according to a pre-defined priority(e.g., defined by the relevant standard). In some designs, thepre-defined order may be based on an associated sub-report periodicity(e.g., aperiodic/semi-persistent/periodic (A/SP/P) over PUSCH/PUCCH),measurement type (e.g., L1-RSRP or not), serving cell index (e.g., incarrier aggregation (CA) case), and reportconfigID. With 2-part CSIreporting, the part 1s of all reports are grouped together, and the part2s are grouped separately, and each group is separately encoded (e.g.,part 1 payload size is fixed based on configuration parameters, whilepart 2 size is variable and depends on configuration parameters and alsoon associated part 1 content). A number of coded bits/symbols to beoutput after encoding and rate-matching is computed based on a number ofinput bits and beta factors, per the relevant standard. Linkages (e.g.,time offsets) are defined between instances of RSs being measured andcorresponding reporting. In some designs, CSI-like reporting ofPRS-based measurement data using L1 and L2 signaling may be implemented.

FIG. 6 illustrates an exemplary wireless communications system 600according to various aspects of the disclosure. In the example of FIG. 6, a UE 604, which may correspond to any of the UEs described above withrespect to FIG. 1 (e.g., UEs 104, UE 182, UE 190, etc.), is attemptingto calculate an estimate of its position, or assist another entity(e.g., a base station or core network component, another UE, a locationserver, a third party application, etc.) to calculate an estimate of itsposition. The UE 604 may communicate wirelessly with a plurality of basestations 602 a-d (collectively, base stations 602), which may correspondto any combination of base stations 102 or 180 and/or WLAN AP 150 inFIG. 1 , using RF signals and standardized protocols for the modulationof the RF signals and the exchange of information packets. By extractingdifferent types of information from the exchanged RF signals, andutilizing the layout of the wireless communications system 600 (i.e.,the base stations locations, geometry, etc.), the UE 604 may determineits position, or assist in the determination of its position, in apredefined reference coordinate system. In an aspect, the UE 604 mayspecify its position using a two-dimensional coordinate system; however,the aspects disclosed herein are not so limited, and may also beapplicable to determining positions using a three-dimensional coordinatesystem, if the extra dimension is desired. Additionally, while FIG. 6illustrates one UE 604 and four base stations 602, as will beappreciated, there may be more UEs 604 and more or fewer base stations602.

To support position estimates, the base stations 602 may be configuredto broadcast reference RF signals (e.g., Positioning Reference Signals(PRS), Cell-specific Reference Signals (CRS), Channel State InformationReference Signals (CSI-RS), synchronization signals, etc.) to UEs 604 intheir coverage areas to enable a UE 604 to measure reference RF signaltiming differences (e.g., OTDOA or reference signal time difference(RSTD)) between pairs of network nodes and/or to identify the beam thatbest excite the LOS or shortest radio path between the UE 604 and thetransmitting base stations 602. Identifying the LOS/shortest pathbeam(s) is of interest not only because these beams can subsequently beused for OTDOA measurements between a pair of base stations 602, butalso because identifying these beams can directly provide somepositioning information based on the beam direction. Moreover, thesebeams can subsequently be used for other position estimation methodsthat require precise ToA, such as round-trip time estimation basedmethods.

As used herein, a “network node” may be a base station 602, a cell of abase station 602, a remote radio head, an antenna of a base station 602,where the locations of the antennas of a base station 602 are distinctfrom the location of the base station 602 itself, or any other networkentity capable of transmitting reference signals. Further, as usedherein, a “node” may refer to either a network node or a UE.

A location server (e.g., location server 230) may send assistance datato the UE 604 that includes an identification of one or more neighborcells of base stations 602 and configuration information for referenceRF signals transmitted by each neighbor cell. Alternatively, theassistance data can originate directly from the base stations 602themselves (e.g., in periodically broadcasted overhead messages, etc.).Alternatively, the UE 604 can detect neighbor cells of base stations 602itself without the use of assistance data. The UE 604 (e.g., based inpart on the assistance data, if provided) can measure and (optionally)report the OTDOA from individual network nodes and/or RSTDs betweenreference RF signals received from pairs of network nodes. Using thesemeasurements and the known locations of the measured network nodes(i.e., the base station(s) 602 or antenna(s) that transmitted thereference RF signals that the UE 604 measured), the UE 604 or thelocation server can determine the distance between the UE 604 and themeasured network nodes and thereby calculate the location of the UE 604.

The term “position estimate” is used herein to refer to an estimate of aposition for a UE 604, which may be geographic (e.g., may comprise alatitude, longitude, and possibly altitude) or civic (e.g., may comprisea street address, building designation, or precise point or area withinor nearby to a building or street address, such as a particular entranceto a building, a particular room or suite in a building, or a landmarksuch as a town square). A position estimate may also be referred to as a“location,” a “position,” a “fix,” a “position fix,” a “location fix,” a“location estimate,” a “fix estimate,” or by some other term. The meansof obtaining a location estimate may be referred to generically as“positioning,” “locating,” or “position fixing.” A particular solutionfor obtaining a position estimate may be referred to as a “positionsolution.” A particular method for obtaining a position estimate as partof a position solution may be referred to as a “position method” or as a“positioning method.”

The term “base station” may refer to a single physical transmissionpoint or to multiple physical transmission points that may or may not beco-located. For example, where the term “base station” refers to asingle physical transmission point, the physical transmission point maybe an antenna of the base station (e.g., base station 602) correspondingto a cell of the base station. Where the term “base station” refers tomultiple co-located physical transmission points, the physicaltransmission points may be an array of antennas (e.g., as in a MIMOsystem or where the base station employs beamforming) of the basestation. Where the term “base station” refers to multiple non-co-locatedphysical transmission points, the physical transmission points may be aDistributed Antenna System (DAS) (a network of spatially separatedantennas connected to a common source via a transport medium) or aRemote Radio Head (RRH) (a remote base station connected to a servingbase station). Alternatively, the non-co-located physical transmissionpoints may be the serving base station receiving the measurement reportfrom the UE (e.g., UE 604) and a neighbor base station whose referenceRF signals the UE is measuring. Thus, FIG. 6 illustrates an aspect inwhich base stations 602 a and 602 b form a DAS/RRH 620. For example, thebase station 602 a may be the serving base station of the UE 604 and thebase station 602 b may be a neighbor base station of the UE 604. Assuch, the base station 602 b may be the RRH of the base station 602 a.The base stations 602 a and 602 b may communicate with each other over awired or wireless link 622.

To accurately determine the position of the UE 604 using the OTDOAsand/or RSTDs between RF signals received from pairs of network nodes,the UE 604 needs to measure the reference RF signals received over theLOS path (or the shortest NLOS path where an LOS path is not available),between the UE 604 and a network node (e.g., base station 602, antenna).However, RF signals travel not only by the LOS/shortest path between thetransmitter and receiver, but also over a number of other paths as theRF signals spread out from the transmitter and reflect off other objectssuch as hills, buildings, water, and the like on their way to thereceiver. Thus, FIG. 6 illustrates a number of LOS paths 610 and anumber of NLOS paths 612 between the base stations 602 and the UE 604.Specifically, FIG. 6 illustrates base station 602 a transmitting over anLOS path 610 a and an NLOS path 612 a, base station 602 b transmittingover an LOS path 610 b and two NLOS paths 612 b, base station 602 ctransmitting over an LOS path 610 c and an NLOS path 612 c, and basestation 602 d transmitting over two NLOS paths 612 d. As illustrated inFIG. 6 , each NLOS path 612 reflects off some object 630 (e.g., abuilding). As will be appreciated, each LOS path 610 and NLOS path 612transmitted by a base station 602 may be transmitted by differentantennas of the base station 602 (e.g., as in a MIMO system), or may betransmitted by the same antenna of a base station 602 (therebyillustrating the propagation of an RF signal). Further, as used herein,the term “LOS path” refers to the shortest path between a transmitterand receiver, and may not be an actual LOS path, but rather, theshortest NLOS path.

In an aspect, one or more of base stations 602 may be configured to usebeamforming to transmit RF signals. In that case, some of the availablebeams may focus the transmitted RF signal along the LOS paths 610 (e.g.,the beams produce highest antenna gain along the LOS paths) while otheravailable beams may focus the transmitted RF signal along the NLOS paths612. A beam that has high gain along a certain path and thus focuses theRF signal along that path may still have some RF signal propagatingalong other paths; the strength of that RF signal naturally depends onthe beam gain along those other paths. An “RF signal” comprises anelectromagnetic wave that transports information through the spacebetween the transmitter and the receiver. As used herein, a transmittermay transmit a single “RF signal” or multiple “RF signals” to areceiver. However, as described further below, the receiver may receivemultiple “RF signals” corresponding to each transmitted RF signal due tothe propagation characteristics of RF signals through multipathchannels.

Where a base station 602 uses beamforming to transmit RF signals, thebeams of interest for data communication between the base station 602and the UE 604 will be the beams carrying RF signals that arrive at UE604 with the highest signal strength (as indicated by, e.g., theReceived Signal Received Power (RSRP) or SINR in the presence of adirectional interfering signal), whereas the beams of interest forposition estimation will be the beams carrying RF signals that excitethe shortest path or LOS path (e.g., an LOS path 610). In some frequencybands and for antenna systems typically used, these will be the samebeams. However, in other frequency bands, such as mmW, where typically alarge number of antenna elements can be used to create narrow transmitbeams, they may not be the same beams. As described below with referenceto FIG. 7 , in some cases, the signal strength of RF signals on the LOSpath 610 may be weaker (e.g., due to obstructions) than the signalstrength of RF signals on an NLOS path 612, over which the RF signalsarrive later due to propagation delay.

FIG. 7 illustrates an exemplary wireless communications system 700according to various aspects of the disclosure. In the example of FIG. 7, a UE 704, which may correspond to UE 604 in FIG. 6 , is attempting tocalculate an estimate of its position, or to assist another entity(e.g., a base station or core network component, another UE, a locationserver, a third party application, etc.) to calculate an estimate of itsposition. The UE 704 may communicate wirelessly with a base station 702,which may correspond to one of base stations 602 in FIG. 6 , using RFsignals and standardized protocols for the modulation of the RF signalsand the exchange of information packets.

As illustrated in FIG. 7 , the base station 702 is utilizing beamformingto transmit a plurality of beams 711-715 of RF signals. Each beam711-715 may be formed and transmitted by an array of antennas of thebase station 702. Although FIG. 7 illustrates a base station 702transmitting five beams 711-715, as will be appreciated, there may bemore or fewer than five beams, beam shapes such as peak gain, width, andside-lobe gains may differ amongst the transmitted beams, and some ofthe beams may be transmitted by a different base station.

A beam index may be assigned to each of the plurality of beams 711-715for purposes of distinguishing RF signals associated with one beam fromRF signals associated with another beam. Moreover, the RF signalsassociated with a particular beam of the plurality of beams 711-715 maycarry a beam index indicator. A beam index may also be derived from thetime of transmission, e.g., frame, slot and/or OFDM symbol number, ofthe RF signal. The beam index indicator may be, for example, a three-bitfield for uniquely distinguishing up to eight beams. If two different RFsignals having different beam indices are received, this would indicatethat the RF signals were transmitted using different beams. If twodifferent RF signals share a common beam index, this would indicate thatthe different RF signals are transmitted using the same beam. Anotherway to describe that two RF signals are transmitted using the same beamis to say that the antenna port(s) used for the transmission of thefirst RF signal are spatially quasi-collocated with the antenna port(s)used for the transmission of the second RF signal.

In the example of FIG. 7 , the UE 704 receives an NLOS data stream 723of RF signals transmitted on beam 713 and an LOS data stream 724 of RFsignals transmitted on beam 714. Although FIG. 7 illustrates the NLOSdata stream 723 and the LOS data stream 724 as single lines (dashed andsolid, respectively), as will be appreciated, the NLOS data stream 723and the LOS data stream 724 may each comprise multiple rays (i.e., a“cluster”) by the time they reach the UE 704 due, for example, to thepropagation characteristics of RF signals through multipath channels.For example, a cluster of RF signals is formed when an electromagneticwave is reflected off of multiple surfaces of an object, and reflectionsarrive at the receiver (e.g., UE 704) from roughly the same angle, eachtravelling a few wavelengths (e.g., centimeters) more or less thanothers. A “cluster” of received RF signals generally corresponds to asingle transmitted RF signal.

In the example of FIG. 7 , the NLOS data stream 723 is not originallydirected at the UE 704, although, as will be appreciated, it could be,as are the RF signals on the NLOS paths 612 in FIG. 6 . However, it isreflected off a reflector 740 (e.g., a building) and reaches the UE 704without obstruction, and therefore, may still be a relatively strong RFsignal. In contrast, the LOS data stream 724 is directed at the UE 704but passes through an obstruction 730 (e.g., vegetation, a building, ahill, a disruptive environment such as clouds or smoke, etc.), which maysignificantly degrade the RF signal. As will be appreciated, althoughthe LOS data stream 724 is weaker than the NLOS data stream 723, the LOSdata stream 724 will arrive at the UE 704 before the NLOS data stream723 because it follows a shorter path from the base station 702 to theUE 704.

As noted above, the beam of interest for data communication between abase station (e.g., base station 702) and a UE (e.g., UE 704) is thebeam carrying RF signals that arrives at the UE with the highest signalstrength (e.g., highest RSRP or SINR), whereas the beam of interest forposition estimation is the beam carrying RF signals that excite the LOSpath and that has the highest gain along the LOS path amongst all otherbeams (e.g., beam 714). That is, even if beam 713 (the NLOS beam) wereto weakly excite the LOS path (due to the propagation characteristics ofRF signals, even though not being focused along the LOS path), that weaksignal, if any, of the LOS path of beam 713 may not be as reliablydetectable (compared to that from beam 714), thus leading to greatererror in performing a positioning measurement.

While the beam of interest for data communication and the beam ofinterest for position estimation may be the same beams for somefrequency bands, for other frequency bands, such as mmW, they may not bethe same beams. As such, referring to FIG. 7 , where the UE 704 isengaged in a data communication session with the base station 702 (e.g.,where the base station 702 is the serving base station for the UE 704)and not simply attempting to measure reference RF signals transmitted bythe base station 702, the beam of interest for the data communicationsession may be the beam 713, as it is carrying the unobstructed NLOSdata stream 723. The beam of interest for position estimation, however,would be the beam 714, as it carries the strongest LOS data stream 724,despite being obstructed.

FIG. 8A is a graph 800A showing the RF channel response at a receiver(e.g., UE 704) over time according to aspects of the disclosure. Underthe channel illustrated in FIG. 8A, the receiver receives a firstcluster of two RF signals on channel taps at time T1, a second clusterof five RF signals on channel taps at time T2, a third cluster of fiveRF signals on channel taps at time T3, and a fourth cluster of four RFsignals on channel taps at time T4. In the example of FIG. 8A, becausethe first cluster of RF signals at time T1 arrives first, it is presumedto be the LOS data stream (i.e., the data stream arriving over the LOSor the shortest path), and may correspond to the LOS data stream 724.The third cluster at time T3 is comprised of the strongest RF signals,and may correspond to the NLOS data stream 723. Seen from thetransmitter's side, each cluster of received RF signals may comprise theportion of an RF signal transmitted at a different angle, and thus eachcluster may be said to have a different angle of departure (AoD) fromthe transmitter. FIG. 8B is a diagram 800B illustrating this separationof clusters in AoD. The RF signal transmitted in AoD range 802 a maycorrespond to one cluster (e.g., “Cluster1”) in FIG. 8A, and the RFsignal transmitted in AoD range 802 b may correspond to a differentcluster (e.g., “Cluster3”) in FIG. 8A. Note that although AoD ranges ofthe two clusters depicted in FIG. 8B are spatially isolated, AoD rangesof some clusters may also partially overlap even though the clusters areseparated in time. For example, this may arise when two separatebuildings at same AoD from the transmitter reflect the signal towardsthe receiver. Note that although FIG. 8A illustrates clusters of two tofive channel taps (or “peaks”), as will be appreciated, the clusters mayhave more or fewer than the illustrated number of channel taps.

RAN1 NR may define UE measurements on DL reference signals (e.g., forserving, reference, and/or neighboring cells) applicable for NRpositioning, including DL reference signal time difference (RSTD)measurements for NR positioning, DL RSRP measurements for NRpositioning, and UE Rx-Tx (e.g., a hardware group delay from signalreception at UE receiver to response signal transmission at UEtransmitter, e.g., for time difference measurements for NR positioning,such as RTT).

RAN1 NR may define gNB measurements based on UL reference signalsapplicable for NR positioning, such as relative UL time of arrival(RTOA) for NR positioning, UL AoA measurements (e.g., including Azimuthand Zenith Angles) for NR positioning, UL RSRP measurements for NRpositioning, and gNB Rx-Tx (e.g., a hardware group delay from signalreception at gNB receiver to response signal transmission at gNBtransmitter, e.g., for time difference measurements for NR positioning,such as RTT).

FIG. 9 is a diagram 900 showing exemplary timings of RTT measurementsignals exchanged between a base station 902 (e.g., any of the basestations described herein) and a UE 904 (e.g., any of the UEs describedherein), according to aspects of the disclosure. In the example of FIG.9 , the base station 902 sends an RTT measurement signal 910 (e.g., PRS,NRS, CRS, CSI-RS, etc.) to the UE 904 at time t₁. The RTT measurementsignal 910 has some propagation delay T_(prop) as it travels from thebase station 902 to the UE 904. At time t₂ (the ToA of the RTTmeasurement signal 910 at the UE 904), the UE 904 receives/measures theRTT measurement signal 910. After some UE processing time, the UE 904transmits an RTT response signal 920 at time t₃. After the propagationdelay T_(prop), the base station 902 receives/measures the RTT responsesignal 920 from the UE 904 at time t₄ (the ToA of the RTT responsesignal 920 at the base station 902).

In order to identify the ToA (e.g., t₂) of a reference signal (e.g., anRTT measurement signal 910) transmitted by a given network node (e.g.,base station 902), the receiver (e.g., UE 904) first jointly processesall the resource elements (REs) on the channel on which the transmitteris transmitting the reference signal, and performs an inverse Fouriertransform to convert the received reference signals to the time domain.The conversion of the received reference signals to the time domain isreferred to as estimation of the channel energy response (CER). The CERshows the peaks on the channel over time, and the earliest “significant”peak should therefore correspond to the ToA of the reference signal.Generally, the receiver will use a noise-related quality threshold tofilter out spurious local peaks, thereby presumably correctlyidentifying significant peaks on the channel. For example, the receivermay choose a ToA estimate that is the earliest local maximum of the CERthat is at least X dB higher than the median of the CER and a maximum YdB lower than the main peak on the channel. The receiver determines theCER for each reference signal from each transmitter in order todetermine the ToA of each reference signal from the differenttransmitters.

In some designs, the RTT response signal 920 may explicitly include thedifference between time t₃ and time t₂ (i.e., T_(Rx→Tx) 912). Using thismeasurement and the difference between time t₄ and time t₁ (i.e.,T_(Tx→Rx) 922), the base station 902 (or other positioning entity, suchas location server 230, LMF 270) can calculate the distance to the

$d = {{\frac{1}{2c}\left( {T_{{Tx}\rightarrow{Rx}} - T_{{Rx}\rightarrow{Tx}}} \right)} = {{\frac{1}{2c}\left( {t_{2} - t_{1}} \right)} - {\frac{1}{2c}\left( {t_{4} - t_{3}} \right)}}}$

where c is the speed of light. While not illustrated expressly in FIG. 9, an additional source of delay or error may be due to UE and gNBhardware group delay for position location.

Various parameters associated with positioning can impact powerconsumption at the UE. Knowledge of such parameters can be used toestimate (or model) the UE power consumption. By accurately modeling thepower consumption of the UE, various power saving features and/orperformance enhancing features can be utilized in a predictive manner soas to improve the user experience.

An additional source of delay or error is due to UE and gNB hardwaregroup delay for position location. FIG. 10 illustrates a diagram 1000showing exemplary timings of RTT measurement signals exchanged between abase station (gNB) (e.g., any of the base stations described herein) anda UE (e.g., any of the UEs described herein), according to aspects ofthe disclosure. FIG. 10 is similar in some respects to FIG. 9 . However,in FIG. 10, the UE and gNB hardware group delay (which is primarily dueto internal hardware delays between a baseband (BB) component andantenna (ANT) at the UE and gNB) is shown with respect 1002-1008. Aswill be appreciated, both Tx-side and Rx-side path-specific orbeam-specific delays impact the RTT measurement. Hardware group delayssuch as 1002-1008 can contribute to timing errors and/or calibrationerrors that can impact RTT as well as other measurements such as TDOA,RSTD, and so on, which in turn can impact positioning performance. Forexample, in some designs, 10 nsec of error will introduce the 3 meter oferror in the final fix.

FIG. 11 illustrates an exemplary wireless communications system 1100according to aspects of the disclosure. In the example of FIG. 11 , a UE1104 (which may correspond to any of the UEs described herein) isattempting to calculate an estimate of its position, or assist anotherentity (e.g., a base station or core network component, another UE, alocation server, a third party application, etc.) to calculate anestimate of its position, via a multi-RTT positioning scheme. The UE1104 may communicate wirelessly with a plurality of base stations1102-1, 1102-2, and 1102-3 (collectively, base stations 1102, and whichmay correspond to any of the base stations described herein) using RFsignals and standardized protocols for the modulation of the RF signalsand the exchange of information packets. By extracting different typesof information from the exchanged RF signals, and utilizing the layoutof the wireless communications system 1100 (i.e., the base stations'locations, geometry, etc.), the UE 1104 may determine its position, orassist in the determination of its position, in a predefined referencecoordinate system. In an aspect, the UE 1104 may specify its positionusing a two-dimensional coordinate system; however, the aspectsdisclosed herein are not so limited, and may also be applicable todetermining positions using a three-dimensional coordinate system, ifthe extra dimension is desired. Additionally, while FIG. 11 illustratesone UE 1104 and three base stations 1102, as will be appreciated, theremay be more UEs 1104 and more base stations 1102.

To support position estimates, the base stations 1102 may be configuredto broadcast reference RF signals (e.g., PRS, NRS, CRS, TRS, CSI-RS,PSS, SSS, etc.) to UEs 1104 in their coverage area to enable a UE 1104to measure characteristics of such reference RF signals. For example,the UE 1104 may measure the ToA of specific reference RF signals (e.g.,PRS, NRS, CRS, CSI-RS, etc.) transmitted by at least three differentbase stations 1102 and may use the RTT positioning method to reportthese ToAs (and additional information) back to the serving base station1102 or another positioning entity (e.g., location server 230, LMF 270).

In an aspect, although described as the UE 1104 measuring reference RFsignals from a base station 1102, the UE 1104 may measure reference RFsignals from one of multiple cells supported by a base station 1102.Where the UE 1104 measures reference RF signals transmitted by a cellsupported by a base station 1102, the at least two other reference RFsignals measured by the UE 1104 to perform the RTT procedure would befrom cells supported by base stations 1102 different from the first basestation 1102 and may have good or poor signal strength at the UE 1104.

In order to determine the position (x, y) of the UE 1104, the entitydetermining the position of the UE 1104 needs to know the locations ofthe base stations 1102, which may be represented in a referencecoordinate system as (x_(k), y_(k)), where k=1, 2, 3 in the example ofFIG. 11 . Where one of the base stations 1102 (e.g., the serving basestation) or the UE 1104 determines the position of the UE 1104, thelocations of the involved base stations 1102 may be provided to theserving base station 1102 or the UE 1104 by a location server withknowledge of the network geometry (e.g., location server 230, LMF 270).Alternatively, the location server may determine the position of the UE1104 using the known network geometry.

Either the UE 1104 or the respective base station 1102 may determine thedistance (d_(k), where k=1, 2, 3) between the UE 1104 and the respectivebase station 1102. In an aspect, determining the RTT 1110 of signalsexchanged between the UE 1104 and any base station 1102 can be performedand converted to a distance (d_(k)). As discussed further below, RTTtechniques can measure the time between sending a signaling message(e.g., reference RF signals) and receiving a response. These methods mayutilize calibration to remove any processing delays. In someenvironments, it may be assumed that the processing delays for the UE1104 and the base stations 1102 are the same. However, such anassumption may not be true in practice.

Once each distance d_(k) is determined, the UE 1104, a base station1102, or the location server (e.g., location server 230, LMF 270) cansolve for the position (x, y) of the UE 1104 by using a variety of knowngeometric techniques, such as, for example, trilateration. From FIG. 11, it can be seen that the position of the UE 1104 ideally lies at thecommon intersection of three semicircles, each semicircle being definedby radius dk and center (x_(k), y_(k)), where k=1, 2, 3.

In some instances, additional information may be obtained in the form ofan angle of arrival (AoA) or angle of departure (AoD) that defines astraight line direction (e.g., which may be in a horizontal plane or inthree dimensions) or possibly a range of directions (e.g., for the UE1104 from the location of a base station 1102). The intersection of thetwo directions at or near the point (x, y) can provide another estimateof the location for the UE 1104.

A position estimate (e.g., for a UE 1104) may be referred to by othernames, such as a location estimate, location, position, position fix,fix, or the like. A position estimate may be geodetic and comprisecoordinates (e.g., latitude, longitude, and possibly altitude) or may becivic and comprise a street address, postal address, or some otherverbal description of a location. A position estimate may further bedefined relative to some other known location or defined in absoluteterms (e.g., using latitude, longitude, and possibly altitude). Aposition estimate may include an expected error or uncertainty (e.g., byincluding an area or volume within which the location is expected to beincluded with some specified or default level of confidence).

FIG. 12 illustrates is a diagram 1200 showing exemplary timings of RTTmeasurement signals exchanged between a base station (e.g., any of thebase stations described herein) and a UE (e.g., any of the UEs describedherein), according to other aspects of the disclosure. In particular,1202-1204 of FIG. 12 denote portions of frame delay that are associatedwith a Rx-Tx differences as measured at the gNB and UE, respectively.

As will be appreciated from the disclosure above, NR native positioningtechnologies supported in 5G NR include DL-only positioning schemes(e.g., DL-TDOA, DL-AoD, etc.), UL-only positioning schemes (e.g.,UL-TDOA, UL-AoA), and DL+UL positioning schemes (e.g., RTT with one ormore neighboring base stations, or multi-RTT). In addition, EnhancedCell-ID (E-CID) based on radio resource management (RRM) measurements issupported in 5G NR Rel-16.

Differential RTT is another positioning scheme, whereby a difference oftwo RTT measurements (or measurement ranges) is used to generate apositioning estimate for a UE. As an example, RTT can be estimatedbetween a UE and two gNBs. The positioning estimate for the UE can thenbe narrowed to the intersection of a geographic range that maps to thesetwo RTTs (e.g., to a hyperbola). RTTs to additional gNBs (or toparticular TRPs of such gNBs) can further narrow (or refine) thepositioning estimate for the UE.

In some designs, a positioning engine (e.g., at the UE, base station, orserver/LMF) can select between whether RTT measurements are to be usedto compute a positioning estimate using typical RTT or differential RTT.For example, if the positioning engine receives RTTs that are known tohave already accounted for hardware group delays, then typical RTTpositioning is performed (e.g., as shown in FIGS. 6-7 ). Otherwise, insome designs, differential RTT is performed so that the hardware groupdelay can be canceled out. In some designs where the positioning engineis implemented at the network-side (e.g., gNB/LMU/eSMLC/LMF), the grouphardware delay at the UE is not known (and vice versa).

FIG. 13 illustrates a diagram 1300 depicting a satellite-basedpositioning scheme. In FIG. 13 , a GPS satellite 1302, a GPS receiver1306 and a GPS receiver 1308 are depicted. GPS satellite 1302 transmitsa GPS signal on a respective path 1310 with phase P^(a) _(q)(t₁) to GPSreceiver 1306, and on a respective path 1312 with phase P^(a) _(r)(t₁)toGPS receiver 1308, whereby

Δp=Δρ+Δdρ−cΔdT+Δd _(ion) +Δd _(trop)+ε_(Δp)   Equation (2)

Δφ=Δρ+Δdρ+cΔdT+λΔN−Δd _(ion) +Δd _(trop)+ε_(Δφ)  Equation (3)

whereby dt denotes satellite clock error, dρ denotes satellite orbitalerror, d_(ion) denotes an ionospheric effect and d_(trop) denotes atropospheric effect.

In FIG. 13 , GPS receiver 1306 may correspond to a base station and GPSreceiver 1308 may correspond to a rover station. In this case, the basestation measurement is subtracted from the rover station measurement forthe same satellite 1302 so as to eliminate satellite clock error dt,reduce the satellite orbital error dρ as a function baseline length, andreduce the ionospheric and tropospheric effect, d_(ion) and d_(trop) asa function of baseline length.

FIG. 14 illustrates a diagram 1400 depicting another satellite-basedpositioning scheme. In FIG. 14 , a GPS satellite 1402, a GPS satellite1404, and a GPS receiver 1406 are depicted. GPS satellite 1402 transmitsa GPS signal on a respective path 1410 with phase P^(a) _(q)(t₁) to GPSreceiver 1406, and GPS satellite 1404 transmits a GPS signal on arespective path 1414 with phase P^(b) _(q)(t₁) to GPS receiver 1406,whereby

∇p=∇ρ+∇dρ+c∇dt++∇d _(ion) +∇d _(trop)+ε_(∇p)   Equation (4)

∇φ=∇ρ+∇dρ+c∇dt+λ∇N−∇d _(ion) +∇d _(trop)+∃_(∇φ)  Equation (5)

In FIG. 14 , a satellite measurement may be subtracted from a basesatellite measurement for the same GPS receiver so as to eliminatesatellite clock error dT, and to reduce a common hardware bias in theGPS receiver 1406.

FIG. 15 illustrates a diagram 1500 depicting another satellite-basedpositioning scheme. In FIG. 15 , a GPS satellite 1502, a GPS satellite1504, a GPS receiver 1506 and a GPS receiver 1508 are depicted. GPSsatellite 1502 transmits a GPS signal on a first path 1510 with phaseP^(a) _(q)(t₁) to GPS receiver 1506, and on a second path 1512 withphase P^(a) _(q)(t₁) to GPS receiver 1508. GPS satellite 1504 transmitsa GPS signal on a first path 1514 with phase P^(b) _(q)(t₁) to GPSreceiver 1506, and on a second path 1516 with phase P^(b) _(r)(t₁) toGPS receiver 1508, whereby

∇Δp=∇Δρ+∇Δdρ+∇Δd _(ion) +∇Δd _(trop)+ε_(∇Δp)   Equation (4)

∇Δφp=∇Δρ+∇Δdρ−∇Δd _(ion) +∇Δd _(trop) +λ∇ΔN+ε _(∇Δφ)  Equation (5)

In FIG. 15 , a base station measurement (e.g., GPS receiver 1506) may besubtracted from a rover station measurement (e.g., GPS receiver 1508)for the same satellite, and the difference between these measurementsmay then be taken from a base satellite (e.g., GPS satellite 1502) andmeasurements at other satellites (e.g., GPS satellite 1508), which mayfunction to eliminate the satellite clock error dt and receiver clockerror dT, and reduce the satellite orbital error dρ, the ionospheric andtropospheric effect, d_(ion) and d_(trop). ∇ΔN denotes the doubledifferenced integer ambiguity. For a 20-30 km baseline, the residualerror may typically be less than ½ cycle.

While the UE hardware group delay cancels out with differential RTT, theresidual gNB group delay (which may be denoted as GD_(diff,gNB_2_1) forgNBs 1 and 2, where gNB 1 may correspond to a reference gNB) may remain,which limits the accuracy of RTT-based positioning, e.g.:

GD_(diff,gNB_2_1)=GD_(gNB_2)−GD_(gNB_1)   Equation (6)

whereby GD_(gNB_2) the residual group delay at gNB 2, GD_(gNB_1) is theresidual group delay at the reference gNB (or gNB 1). GD_(gNB_1) iscommon for all differential RTTs.

Aspects of the disclosure are directed to a double-differential RTTscheme, whereby two (or more) differential RTT measurements are obtainedfor positioning of a target UE. For example, one of the differential RTTmeasurements may be used to cancel out (or at least reduce) UE hardwaregroup delay, while another one of the differential RTT measurementsbetween the UE and wireless nodes (e.g., gNBs, or anchor UEs, or acombination thereof) may be used to cancel out (or at least reduce)residual hardware group delay on the side of the wireless nodes (e.g.,gNBs, or anchor UEs, or a combination thereof). Such aspects may providevarious technical advantages, such as more accurate UE positionestimation. Moreover, as used herein, a “hardware group delay” includesa timing group delay that is at least partially attributable to hardware(e.g., which may vary based on environmental conditions such astemperature, humidity, etc.), but may optionally include other timingdelay(s) attributable to factors such as software, firmware, etc.

FIG. 16 illustrates an exemplary process 1600 of wireless communication,according to aspects of the disclosure. In an aspect, the process 1600may be performed by a position estimation entity, which may correspondto a UE such as UE 302 (e.g., for UE-based positioning), a BS or gNBsuch as BS 304 (e.g., for LMF integrated in RAN), or a network entity306 (e.g., core network component such as LMF).

At 1610, the position estimation entity (e.g., receiver 312 or 322 or352 or 362, data bus 382, network interface(s) 380 or 390, etc.) obtainsa first differential RTT measurement based on a first RTT measurementbetween a UE and a first wireless node and a second RTT measurementbetween the UE and a second wireless node. In this case, the UEcorresponds to a target UE for which a positioning estimate is desired,and the first wireless node and the second wireless node have knownlocations. In some designs, the first and/or second wireless nodescorrespond to gNBs, and in other designs, the first and/or secondwireless nodes correspond to UEs (e.g., anchor UEs or reference UEswhich are static or semi-static and/or for which an accurate positioningestimate have been recently acquired).

At 1620, the position estimation entity (e.g., receiver 312 or 322 or352 or 362, data bus 382, network interface(s) 380 or 390, etc.) obtainsa second differential RTT measurement based on a third RTT measurementbetween a third wireless node and the first wireless node and a fourthRTT measurement between the third wireless node and the second wirelessnode. In some designs, the third wireless node need not be in wirelesscommunication range with the UE. In some designs, the third wirelessnode corresponds to a gNB, and in other designs, the third wireless nodemay correspond to a UE (e.g., anchor UE or reference UE which is staticor semi-static and/or for which an accurate positioning estimate hasbeen recently acquired).

At 1630, the position estimation entity (e.g., positioning module 342 or388 or 389, processing system 332 or 384 or 394, etc.) determines apositioning estimate of the UE based at least in part on the firstdifferential RTT measurement and the second differential RTTmeasurement. Algorithmic examples of the determination of 1630 areexplained in more detail below.

FIG. 17 illustrates an example implementation 1700 of the process 1600of FIG. 16 in accordance with an aspect of the disclosure. In FIG. 17 ,a first wireless node 1702, a second wireless node 1704, a UE 1706 and athird wireless node 1708 are depicted. The first wireless node 1702, thesecond wireless node 1704, the third wireless node 1708 mayalternatively be denoted as wireless nodes 1, 2 and 3, respectively, andcorrespond to the first wireless node, the second wireless node and thethird wireless node as referenced with respect to the process 1600 ofFIG. 16 . In FIG. 17 , a first RTT measurement 1710 between the firstwireless node 1702 and UE 1706 is denoted as RTT_(1_UE), a second RTTmeasurement 1712 between the second wireless node 1704 and UE 1706 isdenoted as RTT_(2_UE), a third RTT measurement 1714 between the thirdwireless node 1708 and the first wireless node 1702 is denoted asRTT_(1_3), and a fourth RTT measurement 1716 between the third wirelessnode 1708 and the second wireless node 1704 is denoted as RTT_(2_3). Thefirst through fourth RTT measurements 1710-1716 correspond to examplesof the first through fourth RTT measurements described above withrespect to the process 16 of FIG. 16 .

FIG. 18 illustrates an example implementation 1800 of the process 1600of FIG. 16 in accordance with another aspect of the disclosure.1802-1816 of FIG. 18 are similar to 1702-1716 of FIG. 17 , respectively,except that the first wireless node 1702, the second wireless node 1704,and the third wireless node 1708 are more specifically illustrated asgNBs 1802, 1804 and 1808, respectively, in FIG. 18 . FIGS. 17 and 18 areotherwise the same, and as such FIG. 18 will not be discussed furtherfor the sake of brevity.

FIG. 19 illustrates an example implementation 1900 of the process 1600of FIG. 16 in accordance with another aspect of the disclosure.1902-1916 of FIG. 19 are similar to 1702-1716 of FIG. 17 , respectively,except that the first wireless node 1702 and the second wireless node1704 are more specifically illustrated as gNBs 1802 and 1804,respectively, in FIG. 18 , and the third wireless node 1708 is morespecifically illustrated as UE 1908 in FIG. 19 . FIGS. 17 and 19otherwise the same, and as such FIG. 19 will not be discussed furtherfor the sake of brevity.

An example implementation of calculations that may be performed as partof the determination of 1630 of FIG. 16 will now be described in moredetail. In the example algorithms described below, position estimationis described with respect to a two-dimensional (2D) coordinate systemincluding x and y coordinates for convenience of explanation, and otheraspects may instead map to a three-dimensional (3D) coordinate systemthat further includes a z coordinate in other aspects. A differentialhardware group delay between the first wireless node and the secondwireless node may be derived as follows:

GD_(diff,2_1)=Gd₁−GD₁=RTT_(2_UE)−RTT_(1_UE)−(T _(2_UE))   Equation (7)

whereby GD₂ denotes the hardware group delay of the second wirelessnode, GD₁ denotes the hardware group delay of the first wireless node(e.g., a reference wireless node, such as a reference gNB), and T_(2_UE)denotes a differential between a double propagation time between thesecond wireless node and the UE and a double propagation time betweenthe first wireless node and the UE, e.g.:

T _(2_UE)=2*√{square root over ((x₂−x_(UE))²+(y₂−y_(UE))²/c)}−2*√{squareroot over ((x₁−x_(UE))²+(y₁−y_(UE))²/c)}  Equation (8)

whereby c corresponds to the speed of light, x₂ denotes an x locationcoordinate of the second wireless node, x_(UE) denotes an x locationcoordinate of the UE, y ₂ denotes a y location coordinate of the secondwireless node, y_(UE) denotes a y location coordinate of the UE, x₁denotes an x location coordinate of the first wireless node, and y₁denotes a y location coordinate of the first wireless node.

GD_(diff,2_1) may further be expressed as follows:

GD_(diff,2_1)=Gd₁−GD₁=RTT_(2_2)−RTT_(1_3)−(T _(2_3))   Equation (9)

whereby T_(2_3) denotes a differential between a double propagation timebetween the second wireless node and the third wireless node and adouble propagation time between the first wireless node and the thirdwireless node, e.g.:

T _(2_3)=2*√{square root over ((x₂−x₃)²+(y₂−y₃)²/c)}−2*√{square rootover ((x₁−x₃)²+(y₁−y₃)²/c)}  Equation (10)

whereby x₃ denotes an x location coordinate of the third wireless node,and y₃ denotes a y location coordinate of the third wireless node.

The hardware group delay of the first wireless node and the secondwireless node can then be canceled out, as follows:

T _(2_UE) −T _(2_2)=RTT_(2_UE)−RTT_(1_UE)−(RTT_(2_3)−RTT_(1_3))  Equation (11)

Referring to FIG. 16 , in some designs, the first differential RTTmeasurement may be triggered by the position estimation entityseparately from the second differential RTT measurement. In other words,RTT_(1_3) and RTT_(2_3) need not be performed jointly with RTT_(1_UE)and RTT_(2_UE). In other designs, RTT_(1_3) and RTT_(2_3) may beperformed jointly (or contemporaneously) with RTT_(1_UE) and RTT_(2_UE).For example, if the third wireless node is static or semi-static, thenolder values for RTT_(1_3) and RTT_(2_3) can be leveraged for positionestimation of the UE since the third wireless node is unlikely to havemoved much (if at all) since those measurements were taken. Accordingly,in some designs, the first differential RTT measurement may be triggeredat a first frequency or based on a first triggering event, and thesecond differential RTT measurement may be triggered at a secondfrequency or based on a second triggering event. In some designs, thefirst differential RTT measurement may be triggered in response to adetermination to perform the positioning estimate of the UE, and thesecond differential RTT measurement is triggered in response to adetermination to calibrate a hardware group delay of the first wirelessnode, the second wireless node, or both. For example, the determinationof the positioning estimate of the UE comprises measuring the firstdifferential RTT measurement, and calibrating a hardware group delay ofthe first wireless node, the second wireless node, or both comprisesmeasuring the second differential RTT measurement. In other designs, thesecond differential RTT measurement may be triggered by thedetermination to perform the positioning estimate of the UE (or putanother way, the second differential RTT measurement may be triggered bythe first differential RTT measurement). As noted above, the hardwaregroup delay of the first and/or second wireless nodes need notnecessarily be calibrated for each UE position estimation (e.g.,especially if the third wireless node is static or semi-static).

Referring to FIG. 16 , in some designs, the first wireless node, thesecond wireless node and the third wireless node are associated withrespective known locations before the determination of the positionestimate. In some designs, the first wireless node, the second wirelessnode and the third wireless node comprise one or more base stations, oneor more anchor UEs, or a combination thereof In some designs, the firstwireless node, the second wireless node and the third wireless node eachcorrespond to a respective base station (e.g., as shown in FIG. 18 ). Inan example where the first wireless node, the second wireless node andthe third wireless node are fixed nodes such as base stations, the thirdRTT measurement may be based on one or more PRSs exchanged between thefirst wireless node and the third wireless node on one or more fixed (ordefault) beams, and the fourth RTT measurement is based on at least onePRS exchanged between the second wireless node and the third wirelessnode on at least one fixed (or default) beam, or a combination thereof.In other designs, the first wireless node, the second wireless node andthe third wireless node may each correspond to a respective UE. In otherdesigns, the first wireless node and the second wireless node correspondto base stations and the third wireless node corresponds to an anchor UEassociated with a known location (e.g., as shown in FIG. 19 ). In somedesigns, positioning resources allocated for determination of a locationof the anchor UE are greater than positioning resources used fordetermination of the positioning estimate of the UE (e.g., to ensurethat the anchor UE has a very accurate position estimate since thisposition estimate is then leveraged for positioning of other UEs). Insome designs, the first wireless node, the second wireless node and thethird wireless node comprise one or more positioning reference units(PRUs) (e.g., in this context, any wireless node used such as anchornode, gNB, etc. that is used as a reference device may correspond to aPRU).

Referring to FIG. 16 , in some designs, the third RTT measurement may bebased on a first PRS from the third wireless node to the first wirelessnode and a second PRS from the first wireless node to the third wirelessnode. In some designs, the first PRS and the second PRS are associatedwith the same PRS type. In some designs, the first PRS and the secondPRS comprise at least one single symbol PRS, at least one multi-symbolPRS (e.g., such as a legacy PRS), or a combination thereof. In somedesigns, the fourth RTT measurement is based on a third PRS from thethird wireless node to the second wireless node and a fourth PRS fromthe second wireless node to the third wireless node. The first PRS mayeither be the same or different from the third PRS (e.g., in otherwords, in some cases, the same PRS can be measured by both the firstwireless node and the second wireless node), while the first PRS and thesecond PRS are different. In some designs, the position estimationentity may transmit a message to the first wireless node and the thirdwireless node that indicates whether the first PRS follows the secondPRS or whether the second PRS follows the first PRS. In some designs,the position estimation entity may transmit a message to the firstwireless node and the third wireless node that indicates a PRS resourceto be used for an initial PRS of the third RTT measurement (e.g., sinceeach PRS may be associated with a specific Tx gNB and one or multiple RxgNB). In some designs, the same type of PRS could be used in thebidirectional transmission, e.g., one class of PRS defined, rather PRSand SRS as in the Uu interface.

Referring to FIG. 16 , in some designs, each PRS (e.g., PRS ID) may beassociated with a pair of gNBs (TRP IDs), e.g., each PRS is associatedwith specific Tx/Rx gNB. In a further example, each PRS may beconfigured from a specific frequency layer, which is associated withspecific common parameters (e.g., center frequency, Start PRB, BW, SCS,CP type and comb size). Each PRS may be associated with one Tx gNB andone or multiple Rx gNB. In some designs, there may be an associationbetween multiple PRS resources for the RTT measurement(s). In somedesigns, at least one PRS is for the transmission from gNB1 to gNB2,another PRS is for the transmission between gNB2 and gNB1. These pairsof PRS resources may be associated with one or multiple RTTmeasurement/report. In some designs, if the PRS is associated with oneTx gNB and one Rx gNB. In some designs, the PRS may be associated with afixed narrow beam (e.g., as the gNBs may be fixed). In some designs, ifthe Rx gNB knows the relative direction between the two gNBs, the Rx gNBmay derive the Rx beam based on that information, hence the beammanagement related search could be reduced or eliminated.

Referring to FIG. 16 , in some designs, the first, second, third andfourth RTT measurements and/or the first differential RTT measurementand the second differential RTT measurement are received at the positionestimation entity via one or more measurement reports. In some designs,the one or more measurement reports each indicate, for a respectivemeasurement, a transmission reception point (TRP) identifier a PRSsource identifier, a PRS resource set ID, a frequency layer ID (e.g.,indicating a respective BW and frequency on which the respective PRSmeasurement is conducted), a time stamp, or a combination thereof.

Referring to FIG. 16 , in some designs, the first differential RTTmeasurement is based on at least one additional RTT measurement betweenthe UE and at least one additional wireless node, the seconddifferential RTT measurement is based on one or more additional RTTmeasurements between the third wireless node and one or more additionalwireless nodes, or a combination thereof. For example, additional RTT(s)such as RTT_(4_UE), RTT_(5_UE), etc. can be used to derive thedifferential RTT measurement for UE 1, and/or additional RTT(s) such asRTT_(4_3), RTT_(5_4), etc. can be used to derive the differential RTTmeasurement for the third wireless node.

Referring to FIG. 16 , in some designs, the position estimation entitymay obtain a third differential RTT measurement based on a fifth RTTmeasurement between a fourth wireless node and the first wireless nodeand a sixth RTT measurement between the fourth wireless node and thesecond wireless node, the positioning estimate is further determinedbased at least in part on the third differential RTT measurement. Inthis case, the positioning estimate can be based on yet another doubledifferential RTT measurements involving two other differential RTTmeasurements for a different pair of wireless nodes (e.g., a differentpair of gNBs).

Referring to FIG. 16 , in some designs, the position estimation entitymay receive, from the first wireless node, the second wireless node, orboth, an indication of a first hardware group delay calibrationcapability, and the second differential RTT measurement is performed inresponse to the first hardware group delay calibration capability. Forexample, the first hardware group delay calibration capability may be adynamic indication or a static or semi-static indication. In somedesigns, another positioning estimate for another UE may be determinedbased on a single differential RTT measurement based on wireless nodesinvolved with the another positioning estimate being associated with asecond hardware group delay calibration capability that is more accuratethan the first hardware group delay calibration capability. In otherwords, in some designs, multiple differential RTT measurements are usedspecifically for scenarios where some degree of hardware group delaycalibration is desired between the first wireless node and the secondwireless node, and can be skipped in other scenarios (e.g., recenthardware group delay calibration is already known, etc.).

Referring to FIG. 16 , the hardware group delay calibration capabilitymay be indicated via a one-time capability report. For example, arespective wireless node (e.g., gNB) may report a high-accuracy groupdelay calibration capability, which may prompt the position estimationentity to skip a differential RTT measurement for hardware group delaycalibration involving that respective wireless node. In another example,the hardware group delay calibration capability may be dynamicallyindicated. For example, the hardware group delay calibration error couldchange over some factors, for example, time, frequency, BW, temperature,etc. Hence, a respective wireless node (e.g., gNB) may dynamicallyindicate a respective accuracy level of hardware group delaycalibration. In some designs, multiple levels of hardware group delaycalibration accuracy may be defined, and a respective wireless node(e.g., gNB) may dynamically report a hardware group calibration accuracylevel. For example, if a respective hardware group delay calibrationerror is large (e.g., above threshold), a respective wireless node mayindicate that the LMF should include this respective wireless node inthe double-differential RTT procedure. In another example, a respectivewireless node (e.g., gNB) may dynamically indicate whether adouble-differential RTT is needed without reporting its respectivehardware group delay calibration accuracy level. In some designs, theposition estimation entity (e.g., LMF) may classify two group ofwireless nodes (e.g., gNBs) based on their capability of hardware groupdelay calibration. For example, a wireless node (e.g., gNB) with highaccuracy hardware group delay calibration may conduct regular RTT ordifferential RTT based UE positioning, and a wireless node (e.g., gNB)with low accuracy hardware group delay calibration may conductdouble-differential RTT-based UE positioning.

Referring to FIG. 16 , in some designs, the position estimation entitymay receive, from the first wireless node, the second wireless node, orboth, a request to trigger the second differential RTT measurement forhardware group delay calibration.

Referring to FIG. 16 , in some designs, the position estimation entitymay select the third wireless node for hardware group delay calibrationof the first wireless node and the second wireless node via the secondRTT differential measurement based on one or more parameters. In somedesigns, the one or more parameters may include channel conditionsbetween the third wireless node and the first wireless node and thesecond wireless node. In some designs, the selection of the thirdwireless node is predetermined if each of the first wireless node, thesecond wireless node and the third wireless node are stationary nodes.In other designs, the selection of the third wireless node is dynamic ifone or more of the first wireless node, the second wireless node and thethird wireless node are mobile nodes. However, such parameters can beused for wireless node selection even for fixed gNBs in addition to moremobile anchor UEs in some designs. For example, in a scenario where thefirst wireless node, the second wireless node and the third wirelessnode correspond to fixed gNBs in a dense deployment (e.g., urbanenvironment), there could be blockage between the gNBs, especially inFR2.

In the detailed description above it can be seen that different featuresare grouped together in examples. This manner of disclosure should notbe understood as an intention that the example clauses have morefeatures than are explicitly mentioned in each clause. Rather, thevarious aspects of the disclosure may include fewer than all features ofan individual example clause disclosed. Therefore, the following clausesshould hereby be deemed to be incorporated in the description, whereineach clause by itself can stand as a separate example. Although eachdependent clause can refer in the clauses to a specific combination withone of the other clauses, the aspect(s) of that dependent clause are notlimited to the specific combination. It will be appreciated that otherexample clauses can also include a combination of the dependent clauseaspect(s) with the subject matter of any other dependent clause orindependent clause or a combination of any feature with other dependentand independent clauses. The various aspects disclosed herein expresslyinclude these combinations, unless it is explicitly expressed or can bereadily inferred that a specific combination is not intended (e.g.,contradictory aspects, such as defining an element as both an insulatorand a conductor). Furthermore, it is also intended that aspects of aclause can be included in any other independent clause, even if theclause is not directly dependent on the independent clause.

Implementation examples are described in the following numbered clauses:

Clause 1. A method of operating a position estimation entity,comprising: obtaining a first differential round trip time (RTT)measurement based on a first RTT measurement between a user equipment(UE) and a first wireless node and a second RTT measurement between theUE and a second wireless node; obtaining a second differential RTTmeasurement based on a third RTT measurement between a third wirelessnode and the first wireless node and a fourth RTT measurement betweenthe third wireless node and the second wireless node; and determining apositioning estimate of the UE based at least in part on the firstdifferential RTT measurement and the second differential RTTmeasurement.

Clause 2. The method of clause 1, wherein the first differential RTTmeasurement is triggered by the position estimation entity separatelyfrom the second differential RTT measurement, or the first wirelessnode, the second wireless node and the third wireless node comprise oneor more positioning reference units (PRUs), or a combination thereof.

Clause 3. The method of any of clauses 1 to 2, wherein the firstdifferential RTT measurement is triggered at a first frequency or basedon a first triggering event, and wherein the second differential RTTmeasurement is triggered at a second frequency or based on a secondtriggering event.

Clause 4. The method of clause 3, wherein the first differential RTTmeasurement is triggered in response to a determination to perform thepositioning estimate of the UE, and wherein the second differential RTTmeasurement is triggered in response to a determination to calibrate ahardware group delay of the first wireless node, the second wirelessnode, or both.

Clause 5. The method of any of clauses 1 to 4, wherein the firstwireless node, the second wireless node and the third wireless node areassociated with respective known locations before the determination ofthe position estimate.

Clause 6. The method of any of clauses 1 to 5, wherein the firstwireless node, the second wireless node and the third wireless nodecomprise one or more base stations, one or more anchor user equipments(UEs), or a combination thereof.

Clause 7. The method of clause 6, wherein the first wireless node, thesecond wireless node and the third wireless node each correspond to arespective base station.

Clause 8. The method of clause 7, wherein the third RTT measurement isbased on one or more positioning reference signals (PRSs) exchangedbetween the first wireless node and the third wireless node on one ormore fixed beams, and wherein the fourth RTT measurement is based on atleast one PRS exchanged between the second wireless node and the thirdwireless node on at least one fixed beam, or a combination thereof.

Clause 9. The method of any of clauses 6 to 8, wherein the firstwireless node, the second wireless node and the third wireless node eachcorrespond to a respective UE.

Clause 10. The method of any of clauses 6 to 9, wherein the firstwireless node and the second wireless node correspond to base stationsand the third wireless node corresponds to an anchor UE associated witha known location.

Clause 11. The method of any of clauses 1 to 10, wherein positioningresources allocated for determination of a location of the anchor UE aregreater than positioning resources used for determination of thepositioning estimate of the UE.

Clause 12. The method of any of clauses 1 to 11, wherein the third RTTmeasurement is based on a first positioning reference signal (PRS) fromthe third wireless node to the first wireless node and a second PRS fromthe first wireless node to the third wireless node.

Clause 13. The method of clause 12, wherein the first PRS and the secondPRS are associated with the same PRS type.

Clause 14. The method of any of clauses 12 to 13, wherein the first PRSand the second PRS comprise at least one single symbol PRS, at least onemulti-symbol PRS, or a combination thereof

Clause 15. The method of any of clauses 12 to 14, wherein the fourth RTTmeasurement is based on a third PRS from the third wireless node to thesecond wireless node and a fourth PRS from the second wireless node tothe third wireless node.

Clause 16. The method of clause 15, wherein the first PRS corresponds tothe third PRS, or wherein the first PRS and the second PRS aredifferent.

Clause 17. The method of any of clauses 12 to 16, further comprising:transmitting a message to the first wireless node and the third wirelessnode that indicates whether the first PRS follows the second PRS orwhether the second PRS follows the first PRS.

Clause 18. The method of any of clauses 12 to 17, further comprising:transmitting a message to the first wireless node and the third wirelessnode that indicates a PRS resource to be used for an initial PRS of thethird RTT measurement.

Clause 19. The method of any of clauses 1 to 18, wherein the first,second, third and fourth RTT measurements and/or the first differentialRTT measurement and the second differential RTT measurement are receivedat the position estimation entity via one or more measurement reports.

Clause 20. The method of clause 19, wherein the one or more measurementreports each indicate, for a respective measurement, a transmissionreception point (TRP) identifier a positioning reference signal (PRS)source identifier, a PRS resource set ID, a frequency layer ID, a timestamp, or a combination thereof

Clause 21. The method of any of clauses 1 to 20, wherein the firstdifferential RTT measurement is based on at least one additional RTTmeasurement between the UE and at least one additional wireless node,wherein the second differential RTT measurement is based on one or moreadditional RTT measurements between the third wireless node and one ormore additional wireless nodes, or a combination thereof.

Clause 22. The method of any of clauses 1 to 21, further comprising:obtaining a third differential RTT measurement based on a fifth RTTmeasurement between a fourth wireless node and the first wireless nodeand a sixth RTT measurement between the fourth wireless node and thesecond wireless node, wherein the positioning estimate is furtherdetermined based at least in part on the third differential RTTmeasurement.

Clause 23. The method of any of clauses 1 to 22, further comprising:receiving, from the first wireless node, the second wireless node, orboth, an indication of a first hardware group delay calibrationcapability, wherein the second differential RTT measurement is performedin response to the first hardware group delay calibration capability.

Clause 24. The method of clause 23, wherein the first hardware groupdelay calibration capability is a dynamic indication or a static orsemi-static indication.

Clause 25. The method of any of clauses 23 to 24, wherein anotherpositioning estimate for another UE is determined based on a singledifferential RTT measurement based on wireless nodes involved with theanother positioning estimate being associated with a second hardwaregroup delay calibration capability that is more accurate than the firsthardware group delay calibration capability.

Clause 26. The method of any of clauses 1 to 25, further comprising:receiving, from the first wireless node, the second wireless node, orboth, a request to trigger the second differential RTT measurement forhardware group delay calibration.

Clause 27. The method of any of clauses 1 to 26, further comprising:selecting the third wireless node for hardware group delay calibrationof the first wireless node and the second wireless node via the secondRTT differential measurement based on one or more parameters.

Clause 28. The method of clause 27, wherein the one or more parameterscomprise channel conditions between the third wireless node and thefirst wireless node and the second wireless node.

Clause 29. The method of clause 28, wherein the selection of the thirdwireless node is predetermined if each of the first wireless node, thesecond wireless node and the third wireless node are stationary nodes,and wherein the selection of the third wireless node is dynamic if oneor more of the first wireless node, the second wireless node and thethird wireless node are mobile nodes.

Clause 30. An apparatus comprising a memory and at least one processorcommunicatively coupled to the memory, the memory and the at least oneprocessor configured to perform a method according to any of clauses 1to 29.

Clause 31. An apparatus comprising means for performing a methodaccording to any of clauses 1 to 29.

Clause 32. A non-transitory computer-readable medium storingcomputer-executable instructions, the computer-executable comprising atleast one instruction for causing a computer or processor to perform amethod according to any of clauses 1 to 29.

Those of skill in the art will appreciate that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof

Further, those of skill in the art will appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the aspects disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the aspects disclosed herein may be implemented orperformed with a general purpose processor, a DSP, an ASIC, an FPGA, orother programmable logic device, discrete gate or transistor logic,discrete hardware components, or any combination thereof designed toperform the functions described herein. A general purpose processor maybe a microprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices,e.g., a combination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration.

The methods, sequences and/or algorithms described in connection withthe aspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in random access memory (RAM), flashmemory, read-only memory (ROM), erasable programmable ROM (EPROM),electrically erasable programmable ROM (EEPROM), registers, hard disk, aremovable disk, a CD-ROM, or any other form of storage medium known inthe art. An exemplary storage medium is coupled to the processor suchthat the processor can read information from, and write information to,the storage medium. In the alternative, the storage medium may beintegral to the processor. The processor and the storage medium mayreside in an ASIC. The ASIC may reside in a user terminal (e.g., UE). Inthe alternative, the processor and the storage medium may reside asdiscrete components in a user terminal.

In one or more exemplary aspects, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and Blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

While the foregoing disclosure shows illustrative aspects of thedisclosure, it should be noted that various changes and modificationscould be made herein without departing from the scope of the disclosureas defined by the appended claims. The functions, steps and/or actionsof the method claims in accordance with the aspects of the disclosuredescribed herein need not be performed in any particular order.Furthermore, although elements of the disclosure may be described orclaimed in the singular, the plural is contemplated unless limitation tothe singular is explicitly stated.

1. A method of operating a position estimation entity, comprising:obtaining a first differential round trip time (RTT) measurement basedon a first RTT measurement between a user equipment (UE) and a firstwireless node and a second RTT measurement between the UE and a secondwireless node; obtaining a second differential RTT measurement based ona third RTT measurement between a third wireless node and the firstwireless node and a fourth RTT measurement between the third wirelessnode and the second wireless node; and determining a positioningestimate of the UE based at least in part on the first differential RTTmeasurement and the second differential RTT measurement.
 2. The methodof claim 1, wherein the first differential RTT measurement is triggeredby the position estimation entity separately from the seconddifferential RTT measurement.
 3. The method of claim 1, wherein thefirst differential RTT measurement is triggered at a first frequency orbased on a first triggering event, and wherein the second differentialRTT measurement is triggered at a second frequency or based on a secondtriggering event.
 4. The method of claim 3, wherein the determination ofthe positioning estimate of the UE comprises measuring the firstdifferential RTT measurement, and wherein calibrating a hardware groupdelay of the first wireless node, the second wireless node, or bothcomprises measuring the second differential RTT measurement.
 5. Themethod of claim 1, wherein the first wireless node, the second wirelessnode and the third wireless node are associated with respective knownlocations before the determination of the position estimate.
 6. Themethod of claim 1, wherein the first wireless node, the second wirelessnode and the third wireless node comprise one or more base stations, oneor more anchor user equipments (UEs), or a combination thereof.
 7. Themethod of claim 6, wherein the first wireless node, the second wirelessnode and the third wireless node each correspond to a respective basestation.
 8. The method of claim 7, wherein the third RTT measurement isbased on one or more positioning reference signals (PRSs) exchangedbetween the first wireless node and the third wireless node on one ormore fixed beams, or wherein the fourth RTT measurement is based on atleast one PRS exchanged between the second wireless node and the thirdwireless node on at least one fixed beam, or a combination thereof. 9.The method of claim 6, wherein the first wireless node, the secondwireless node and the third wireless node each correspond to arespective UE.
 10. The method of claim 6, wherein the first wirelessnode and the second wireless node correspond to base stations and thethird wireless node corresponds to an anchor UE associated with a knownlocation.
 11. The method of claim 10, wherein positioning resourcesallocated for determination of a location of the anchor UE are greaterthan positioning resources used for determination of the positioningestimate of the UE.
 12. The method of claim 1, wherein the firstwireless node, the second wireless node and the third wireless nodecomprise one or more positioning reference units (PRUs).
 13. The methodof claim 1, wherein the third RTT measurement is based on a firstpositioning reference signal (PRS) from the third wireless node to thefirst wireless node and a second PRS from the first wireless node to thethird wireless node.
 14. The method of claim 13, wherein the first PRSand the second PRS are associated with the same PRS type.
 15. The methodof claim 13, wherein the first PRS and the second PRS comprise at leastone single symbol PRS, at least one multi-symbol PRS, or a combinationthereof.
 16. The method of claim 13, wherein the fourth RTT measurementis based on a third PRS from the third wireless node to the secondwireless node and a fourth PRS from the second wireless node to thethird wireless node.
 17. The method of claim 16, wherein the first PRScorresponds to the third PRS, or wherein the first PRS and the secondPRS are different.
 18. The method of claim 13, further comprising:transmitting a message to the first wireless node and the third wirelessnode, the message indicating whether the first PRS follows the secondPRS or whether the second PRS follows the first PRS.
 19. The method ofclaim 13, further comprising: transmitting a message to the firstwireless node and the third wireless node, the message indicating a PRSresource to be used for an initial PRS of the third RTT measurement. 20.The method of claim 1, wherein the first, second, third and fourth RTTmeasurements and/or the first differential RTT measurement and thesecond differential RTT measurement are received at the positionestimation entity via one or more measurement reports.
 21. The method ofclaim 20, wherein the one or more measurement reports each indicate, fora respective measurement, a transmission reception point (TRP)identifier a positioning reference signal (PRS) source identifier, a PRSresource set ID, a frequency layer ID, a time stamp, or a combinationthereof.
 22. The method of claim 1, wherein the first differential RTTmeasurement is based on at least one additional RTT measurement betweenthe UE and at least one additional wireless node, wherein the seconddifferential RTT measurement is based on one or more additional RTTmeasurements between the third wireless node and one or more additionalwireless nodes, or a combination thereof.
 23. The method of claim 1,further comprising: obtaining a third differential RTT measurement basedon a fifth RTT measurement between a fourth wireless node and the firstwireless node and a sixth RTT measurement between the fourth wirelessnode and the second wireless node; and using the third differential RTTmeasurement to determine the positioning estimate.
 24. The method ofclaim 1, further comprising: receiving, from the first wireless node,the second wireless node, or both, an indication of a first hardwaregroup delay calibration capability, wherein the second differential RTTmeasurement is triggered in response to the first hardware group delaycalibration capability.
 25. The method of claim 24, wherein the firsthardware group delay calibration capability is a dynamic indication or astatic or semi-static indication.
 26. The method of claim 24, whereinanother positioning estimate for another UE is determined based on asingle differential RTT measurement based on wireless nodes involvedwith the another positioning estimate being associated with a secondhardware group delay calibration capability that is more accurate thanthe first hardware group delay calibration capability.
 27. The method ofclaim 1, further comprising: receiving, from the first wireless node,the second wireless node, or both, a request to trigger the seconddifferential RTT measurement for hardware group delay calibration. 28.The method of claim 1, further comprising: selecting the third wirelessnode for hardware group delay calibration of the first wireless node andthe second wireless node via the second RTT differential measurementbased on one or more parameters.
 29. The method of claim 28, wherein theone or more parameters comprise channel conditions between the thirdwireless node and the first wireless node and the second wireless node.30. The method of claim 29, wherein the selection of the third wirelessnode is predetermined if each of the first wireless node, the secondwireless node and the third wireless node are stationary nodes, andwherein the selection of the third wireless node is dynamic if one ormore of the first wireless node, the second wireless node and the thirdwireless node are mobile nodes.
 31. A position estimation entity,comprising: a memory; at least one transceiver; and at least oneprocessor communicatively coupled to the memory and the at least onetransceiver, the at least one processor configured to: obtain a firstdifferential round trip time (RTT) measurement based on a first RTTmeasurement between a user equipment (UE) and a first wireless node anda second RTT measurement between the UE and a second wireless node;obtain a second differential RTT measurement based on a third RTTmeasurement between a third wireless node and the first wireless nodeand a fourth RTT measurement between the third wireless node and thesecond wireless node; and determine a positioning estimate of the UEbased at least in part on the first differential RTT measurement and thesecond differential RTT measurement.
 32. The position estimation entityof claim 31, wherein the first differential RTT measurement is triggeredby the position estimation entity separately from the seconddifferential RTT measurement.
 33. The position estimation entity ofclaim 31, wherein the first differential RTT measurement is triggered ata first frequency or based on a first triggering event, and wherein thesecond differential RTT measurement is triggered at a second frequencyor based on a second triggering event. 34-60. (canceled)
 61. A positionestimation entity, comprising: means for obtaining a first differentialround trip time (RTT) measurement based on a first RTT measurementbetween a user equipment (UE) and a first wireless node and a second RTTmeasurement between the UE and a second wireless node; means forobtaining a second differential RTT measurement based on a third RTTmeasurement between a third wireless node and the first wireless nodeand a fourth RTT measurement between the third wireless node and thesecond wireless node; and means for determining a positioning estimateof the UE based at least in part on the first differential RTTmeasurement and the second differential RTT measurement.
 62. Theposition estimation entity of claim 61, wherein the first differentialRTT measurement is triggered by the position estimation entityseparately from the second differential RTT measurement.
 63. (canceled)